They have different use cases: with PAKEs you encrypt a connection, not a file. You can’t use PAKEs to encrypt backups. Or, rather, you can but then the two sides just have to store the key, making it not fit for e2ee use cases. It’s password authenticated key exchange, not password derived keys.

(Well, the WhatsApp solution actually uses a PAKE to talk to the HSM, but the HSM is still necessary.)