why do you have to assume that?

you're at Acme Coffeeshop. their wifi password is "greatcoffee" and it's printed next to the cash register where all customers can see it.

with WPA2 you have to consider N possible adversaries - Acme Coffee themselves, as well as every single other person at the coffeeshop.

...and also anyone else within signal range of their AP. maybe I live in an apartment above the coffeeshop, and think "lol it'd be fun to collect all that traffic and see if any of it is unencrypted".

with WPA3 you only have to consider the single possible adversary, the coffeeshop themselves.