> Tend in what way? I can think of perhaps rebalancing so if you're doing a multi-fund setup with particularly desired asset allocation (bonds, equities: US, world, EM). But if you're using (say) a target date fund, what's there to do?
(General response, just quoting this part) - life is messy, things change around you. My 401k for example (throughout different jobs) bounces around, I've had Schwab, WellsFargo, Vanguard (even some no-brand way back when) who each offer their own strategies; some having severely limited options, some having open playing fields - in 2000 WellsFargo may have offered 1 of 3 choices IIRC. In 2020, they have 30 choices (many are target date funds) - but Schwab is open-ended, do what you want; when your money rolls over from one to the other, it's usually a liquidation and cash transfer (although I've used in-kind for a Roth IRA, worked OK but not perfect - lost some cost basis data, had to repair). I do not get to choose where my 401k is hosted in USA, your company chooses the vendor - this may differ up there in Soviet Canuckistan. :)
Some companies shut down their investment division (USAA -> Victory Capital recently), so what was a no-fee no-load option at that company now costs $$ at another company - for example, I think Vanguard funds are free to trade on Vanguard but really expensive on Schwab, so if you held VFINX and rolled it in-kind over to Schwab it would now cost you more than if you unloaded VFINX and replaced it with SWPPX. Some funds are unique to that company and it's hard to find replacements (USAA's USNQX e.g.) so you might choose to eat cross-vendor fees because it's performance is just that good. Really depends on all the "what's free to trade at this vendor" - it's not always an even playing field, each vendor wants to push their in-house flavour of the index.
Different category but related: company stock - for whatever reason, that's almost always been E-Trade (now Morgan Stanley!) in tech; both Google and Red Hat offered friends-of-company shares exclusively though E-Trade, my company does it, etc. - so now I have yet another vendor to deal with and it tends to grow arms and legs unless you keep pulling money out and pushing it over to your preferred vendors. Target funds are actively managed assets, they have higher fees and constant re-balancing being done by humans to meet "the target" - they're still kind of new (many created mid-2010s I think) so we only have so much data, but generally they're 4-star and lag (returns) behind any common 5-star index fund. (compare 2 from the same vendor, for example SWPPX vs SWYGX but almost all vendors have them now, this is not investing advice).
In Canada our 401k-equivalent is the Registered Retirement Saving Plan (RRSP). Most companies have something similar to what you describe in that they hook up with a financial services company and do contribution matching. That company has certain offerings, either mutual fund (often fees/MERs > 1%) or if you're lucky perhaps ETFs nowadays.
I frequent /r/PersonalFinanceCanada and semi-often we get people asking which of the offered mutual funds should someone buy. The general consensus is that for most people to choose the funds that have the lowest fees and closely match a equity or bond index: pick a bond percentage weighting that generally let's you sleep at night.
When you leave a job you can often leave the money with the financial company, but it's often easier to do a liquidate-and-transfer to a 'central' RRSP account if you hope around a lot.
I think the USA is sort of the same, my experience is layperson so I don't know if this is typical or normal: the company itself pays a fee to the vendor to maintain your 401k account under whatever the 401k legalities are (taxes being deferred etc.). A lot of time the funds available to choose from are the "institutional" kind that us mere mortals can't buy, only large vendors. So our money is pool-leveraged at scale using techniques and funds we individuals cannot access.
When you leave that employer, you can leave your 401k at that vendor but after awhile the old company starts to bug you about moving it as it's costing them money to maintain an account for an ex-employee. I missed that subtle point you noted - most companies (? all?) only match contributions to their vendor 401k, so there's our internal-company incentive to get you onto their plan to get those sweet, sweet matching dollars.
(General response, just quoting this part) - life is messy, things change around you. My 401k for example (throughout different jobs) bounces around, I've had Schwab, WellsFargo, Vanguard (even some no-brand way back when) who each offer their own strategies; some having severely limited options, some having open playing fields - in 2000 WellsFargo may have offered 1 of 3 choices IIRC. In 2020, they have 30 choices (many are target date funds) - but Schwab is open-ended, do what you want; when your money rolls over from one to the other, it's usually a liquidation and cash transfer (although I've used in-kind for a Roth IRA, worked OK but not perfect - lost some cost basis data, had to repair). I do not get to choose where my 401k is hosted in USA, your company chooses the vendor - this may differ up there in Soviet Canuckistan. :)
Some companies shut down their investment division (USAA -> Victory Capital recently), so what was a no-fee no-load option at that company now costs $$ at another company - for example, I think Vanguard funds are free to trade on Vanguard but really expensive on Schwab, so if you held VFINX and rolled it in-kind over to Schwab it would now cost you more than if you unloaded VFINX and replaced it with SWPPX. Some funds are unique to that company and it's hard to find replacements (USAA's USNQX e.g.) so you might choose to eat cross-vendor fees because it's performance is just that good. Really depends on all the "what's free to trade at this vendor" - it's not always an even playing field, each vendor wants to push their in-house flavour of the index.
Different category but related: company stock - for whatever reason, that's almost always been E-Trade (now Morgan Stanley!) in tech; both Google and Red Hat offered friends-of-company shares exclusively though E-Trade, my company does it, etc. - so now I have yet another vendor to deal with and it tends to grow arms and legs unless you keep pulling money out and pushing it over to your preferred vendors. Target funds are actively managed assets, they have higher fees and constant re-balancing being done by humans to meet "the target" - they're still kind of new (many created mid-2010s I think) so we only have so much data, but generally they're 4-star and lag (returns) behind any common 5-star index fund. (compare 2 from the same vendor, for example SWPPX vs SWYGX but almost all vendors have them now, this is not investing advice).