Anyone familiar with the history of how PDFs became such a widespread format in the first place? I get that it looks nice but not being able to edit it by default just seems weird to me.
Well, unless you sign the PDF. Even more, you can sign each edit separately, so you can do things like add content and signatures and still verify who added what. Meaning: one party can create PDF with forms, sign it, then the party filling out the form can sign their own changes for authentication.
And let's not forget the fact that PDF renders correctly on pretty much any machine you put it on - this is incredibly important.
But can you edit a properly signed[1] PDF without breaking it? From an integrity perspective, that's what matters; otherwise, it's just inherently more portable until non-repudiation becomes relevant.
[1] As in not SHA-1: https://shattered.io/
I don't think anyone is motivated enough to make that standard, however.