I think the dream is you could have one SSL process that others communicated with. Message passing at large.
Because it's a separate process, so when it crashes your application can put up a "SSL failed, reconnecting" message and carry on. Also when your application has read-something-somewhere security vulnerability, it can't compromise your SSL keys.
Nitpick: it's not one process, but one executable; you can have multiple SSL daemons using the same (read-only) binary, so a attack on one only gets one set of keys. (The same attack will probably work on every instance of the same version of SSLd, but shared objects don't fix that.)