There are a number of things it offers. Being able to play high end triple A games on a chromebook or a cheap computer would be a huge boon. Not everyone wants to(or has the means to) spend 1300+ dollars on a gaming computer. Also there is also the casual market. Even the people who do want to play games and have the money, it's hard to justify the cost if you just play like 1 or 2 games per year. Another huge boon is the ability to switch between devices and places. Going from your television to your office to your laptop, or from your house to a hotel, to a friends house, or whatever has huge amounts of utility.

It lets you play a selection of current games without buying & maintaining expensive on-prem gaming systems, and works on the go as well.

It also promises to have longevity while following latest hardware developments, without having to upgrade your pc or replace your console with this year's hw generation. Of course the uncertainty about the longevity of the Stadia service counters this somewhat.. but the model technically solves longevity which is cool.

I totally understand the draw. No need for equipment, and works on any platform, everywhere. Steam streaming was an interesting game-changer for me, until I gave on it, due to performance concerns. You could play it in every room, on any machine, and it worked pretty darn well; I was impressed.

It solves the problem that Chromebooks can't run good games.

It is only a problem if you work for Google.