They're accounting for the users who will try to play the game with 24 chrome tabs plus photoshop, illustrator, teams and something else open in the background. I used to laugh at these RAM requirements just as you, but since I started working and met (many) people that do this I understood why devs do this. People don't seem to understand what leaving a program open in the background means.
A lot of this comes from modern smartphone usage, since smartphones tend to clear RAM and suspend background apps people seem to think it doesn't matter. I remember youtuber "UrAVGConsumer" once did a video where he shows how many tabs are open on his iphone and he had like 1000 tabs open, I know my mother and father would do the same if I didn't clear their phones from time to time, and i've seen some of my colleagues in a similar situation.
We were just born at a time where this was simply not possible (I suppose) and we since learned not to do it, others either didn't have access to such computing devices, or are simply younger and don't understand it, because they don't have to. And I think there's more of them than there are of us.