It becomes murky when you don’t actually ship software and use it as a service in the backend. GPL is from the olden days when you actually distributed your software. Now it’s only the front end and that ships as source still because wasm and the rest haven’t taken over yet.
AGPL then. It extends the meaning of "distribute", but is still FSF/OSI-approved
AGPL is super scary for corporations, as it's not clear where the boundaries are and no one wants to go to court to find out. GPL is relatively straight forward: as long as you don't link to it, make sources including any changes available to your users.
AGPL is like, okay maybe everything needs to be released. And when you are also using proprietary third party software it becomes a real hairy mess.