Why don’t most websites I visit seem to use TLS with Diffie-Hellman?

When I click “view certificate,” under Public Key Algorithm it usually says “RSA Encryption” or “Elliptic Curve Public Key.” I assume this is the algorithm used to agree on a premaster secret between the client and server. Why not use Diffie-Hellman then? Doesn’t Diffie-Hellman provide forward secrecy?