What I mean is that you (IIUC) can’t use an AGPL library in a GPL app without relicensing the whole thing to AGPL. For many larger projects relicensing is a huge hassle and often a non-starter if there aren’t very good reasons for it.

“just don’t enforce it” probably isn’t enough for most companies and projects

A good reason to pick GPL is if you want to allow GPL software to integrate yours and you don’t care that much about the AGPL clauses (e.g. because your app isn’t a server).

CC0 might be a good fit for trivial template repos where you don’t want to burden downstream projects with having to include copyright notices.