Maybe late to the game (no pun! :)) but ok.

I must say that my last console was a PS3, then I played on steam 2 or 3 times a year, now I was lend a PS4 by a friend cause I wanted to try some exclusivity but is it normal to install 20-30GB even when you own physical game ?

It was already a thing annoying back in the day on PS3 for some game (GTA 5 being the worst as far as remember) but here, it is getting ridiculous and seems to be default behavior for most games.

On PC, which is mostly dematerialized, why not, at least, you can use your computer in during the time but I don’t expect that from a console.