How come ps5 games can’t use ps4 controllers even tho the game was made for both consoles

Whenever I have relatives over I have to use ps4 controllers since I don’t have multiple ps5 ones, and that results with me having to download ps4 versions of the ps5 games I have

I thought that was just a hardware requirement, then I found out that the Nintendo switch 2 could use switch 1 controllers even when the game was designed for the switch 2

How come that isn’t the same for PlayStation, did Sony just not think of it.