Just as with any other X-as-a-service, it quickly becomes cheaper to just buy it outright than to rent it.
And even if the pricing itself isn't that clear-cut, not having the constant stress of "I'm spending $x/h, I had better enjoy every minute of it" (or, on the flip side, "I'm already spending $x/mo, so I need to use it as much as possible") makes it a lot easier to enjoy the experience.
If you play games a lot it will quickly become cheaper to buy a high end PC. But if you're like me and only game a couple hours a week on average, it ends up being cheaper than getting a new top-of-the-line PC every 3 years to continue playing new games on max settings.
Right now it's free.. can't get any cheaper than that. :P
And even if the pricing itself isn't that clear-cut, not having the constant stress of "I'm spending $x/h, I had better enjoy every minute of it" (or, on the flip side, "I'm already spending $x/mo, so I need to use it as much as possible") makes it a lot easier to enjoy the experience.