PS4 Controllers unnecessary for PS5?

Hi all,

Probably a stupid question but cannot seem to find the answer...

I know that DS4 controllers can only be used on a PS5 for PS4 games, but...

Are they necessary for that (I assume no) or for any other reason..?

Or to rephrase, is there any reason to keep DS4 controllers when getting a PS5? (Beyond if you "just like them" or whatever).

Thanks.