Why doesn't pgp/gpg not count? Because it's too difficult to set up? Do you really trust an encryption with automatically generated, non-exchangeable keys?

That said hardly anybody I know still uses e-mail for private communication.

Why doesn't PGP count?

Because it's PGP not email providing the encryption. Say we said PGP does count as e2ee for email, why doesn't it count for RCS? What about every protocol, I can just PGP sign messages on them so aren't they all e2ee?

Ideally when talking about e2ee it's not an optional opt in either but that's a whole different debate.

TLS isn't end-to-end encryption?

Not in email. End-to-end here means that noone except sender and reciever can read the content. With tls and email you send it to a server which can read it, not to the enduser.

No. End to end means that plaintext exists only at the two ends (initial sender, final receiver) of a communication.