Because it's easier to wrap an arbitrary protocol with TLS than it is to tunnel it through ssh. Plus, TLS is already supported for the purposes you mentioned. A

Because it's easier to wrap an arbitrary protocol with TLS than it is to tunnel it through ssh. Plus, TLS is already supported for the purposes you mentioned. A number of MU*s already offer TLS access, IRC and XMPP have supported TLS since forever, there's near ubiquitous support for it in any language you want to write a client/server in, plus, as others have mentioned, you don't have the security risks that SSH can potentially have. It just provides too much weight for not enough benefit.