Honestly? 4ish years of a stadia subscription will run any game released in that time period, and also the entire back catalog of PC gaming, minus some annoyingness around early 2000s games and permissions. My $500 PC runs VR at 1.7x supersampling with zero issues, and can 1080p60hz any game at all with zero trouble.
Four years of a subscription you can pay month-to-month (and cancel if you're not using it) is much more doable for many people than a $500+ upfront investment in a gaming rig. Presumably you also built this yourself at that price point, which is another thing other people are not as willing to do.
For me personally, I travel a lot so I like the idea of Stadia because obviously I'm not going to travel around with a gaming rig, and you can pry my 2015 Macbook Pro from my cold, dead hands.
What kinda of cost are we talking about when you say "low spec"?