You don't get it. Most people just care if the games are free with a $10 a month subscription. By the time PS5/Scarlett comes out 1080/60 will be as outdated as 720/60. PS Now and Gamepass will allow you to download your games directly to the hardware. No streaming required. If given the choice between paying $60 a pop for games on Stadia, and just paying $10 a month plus the cost of hardware most people will choose the option that gets them hundreds of games for $10 a month.
That's the problem you can't play the games on a phone or low-end PC, you need a gaming PC or xbox/scarlett.
Buying a gaming PC, Scarlett, or PS5 and then getting gamepass/PS Now will be cheaper than paying $60-$50 for every single AAA game you want on stadia.