From the beginning, Jerry Seinfeld played the comedian.
After graduating in 1976 from Queens college, he spent a few years of doing standup before landing his first TV “role”: He’d been cast as a recurring character named Frankie on the sitcom Benson (he shows up at 4:06 of this clip below), a mail delivery guy who did comedy routines no one wanted to hear. After three episodes, however, he showed up for a read-through only to find no script waiting with his name on it. It wasn’t until he asked what was going on that an assistant director pulled him aside to tell him: He’d been fired.
Never again, he vowed. This kind of thing couldn’t happen in standup. You could get booed, heckled, or shoved into a terrible timeslot at an open mic, but you could never be cut off or ignored or fired. Besides which, he must have hated playing a guy whose jokes no one wanted to hear.