I think part of the difference is that in gaming if performance sucks then there's a real community of people who push back and it will affect sales directly. In web development at least for the majority of sites (e.g. not on the level of usage of Github) usually people just stop visiting your site, so you don't see public pushback as much.

If a decent portion of your audience literally cannot even play the game because its performance is too bad or it can't run on their hardware, then that immediately affects your bottom line. And at least until recently, you couldn't really push fixes for it once the game was delivered. And so I think at least a little bit of that mindfullness for performance has carried over to the modern day, though I will say that I do think that performance optimization does seem to subjectively be getting worse even in gaming.

In web dev, while it is true that it affects your bottom line, it's a little bit less obvious. And in the eyes of most management teams that's always something that can be prioritized later since you could always update it after you shipped a feature. Also, there was very much a culture of "the browser will handle it."

Not to mention, most devs are using the hardware that is many times better than their consumers.