It’s always seemed to me like a duo worked better in the medium of radio, where there wasn’t a live audience so they could bounce jokes off each other without having to worry about how they looked to the audience.
One of Murphy-St. Paul ( Sue Murphy, Dan St. Paul - can’t remember which one was commenting ) said this point was a particular killer. Duos were often offered the same pay as single acts, not to mention male-female pairings as with the above were often assumed ( wrongly ) to be couples, causing occasional tiresomely touchy issues. During the heyday of standup in and around the 1980’s when comedy clubs were everywhere and pay was good, this was barely tolerable. But once the stand-up bubble popped it became kinda unsustainable economically for workaday comedians.
Jeff Dunham and his various partners do pretty well.