People like it because it offers a HUGE performance increase with little to no VISIBLE quality loss. Have you actually played a game with it enabled?
Yes I played Control with it, both with 1.0 and 2.0. You can even switch it on and off on the fly, so it's easy to compare. Of course it offers a huge performance increase, you're running at half resolution. No I do not agree it offers "no visible quality loss," that's the whole point. It looks obviously much more processed with a smeared look and sharpening artifacts out the wazoo.
If you google you'll find many people agree with me, they're just being drowned out people with less visual pickiness who don't notice such things (or don't care). Movies have gone through the same thing, "let's process the shit out of this DVD master to make it look HD!" Some people don't notice the difference, some people do and fucking hate it. All depends on the person... which is fine, as long as it's just an option. I just don't think it'll be an option forever, either because games will design themselves around it like TAA or performance simply won't be adequate without it.