Where are these regulations from? As in, which country?

> must have at least 2 stairwells, or emergency stairs

The tower in question did not:

https://www.google.com/search?q=grenfell+tower+floor+plan

So it was designed around a stay-where-you-are fire plan, not an immediate evacuation. And this may have been entirely sensible for the design as built -- concrete floors, concrete walls, and I presume serious doors onto the stairs. Then a fire would not spread.

But when you alter this design, then it doesn't work anymore. You can break any design with sufficient modifications; someone has to enforce that you don't.

> Where are these regulations from? As in, which country?

As an adult, I lived in Russia, Singapore, Canada, and China.

Russia for sure has at least half of that in the code.

Singapore, and Canada a bit more, but do not mandate fire extinguishers in residential buildings on national level.

And China has all of the above... on paper.

Can't say I know anything about those, unless Hong Kong counts -- it is certainly full of towers with barely space for one staircase.

From what I heard, HK indeed requires 2 stairs, just no necessary two separate staircases.

Ah, looking again at floorplans, some appear to be stacking two stair paths in one stairwell. So if you have a fire in one apartment, maybe the smoke only reaches (say) even-floor-number front doors.

As as said above, even much better fireproofed buildings may collapse quicky if the circumstances are bad enough.

Fireproofing alone is not a solution.

I think I have not seem a single highrise in my life without 2 staircases, or emergency staircase anywhere, even in very old buildings.

I take it you live in the US, since you're generally describing US fire code regulations, which are not the same as regulations in other countries, and are generally geared far more towards evacuate-first than compartmentalization.