The policy is not restricted to UA/UX crews. If the bins are full, though, it has to be checked.

We used to have a procedure where UA pilots, in unform, could do a self-gate-check. We'd take our bag, with a special tag, down to the designated cargo door and the ramp crew would load it last. On arrival, the ground crew puts the tagged bag aside at the cargo door and we'd go back down to pick it up. That went away because the airports we no longer allowing non-operating crewmembers to access the ramp.