Great stand-ups instinctively know when and how to drop punch lines. It's just part of what they do, like breathing...hitting the punch with born in timing that is beautiful to experience. They also know attitude, character and have plenty of it...but they respect punch lines plain and simple.
Stand-up would have never become an art form without the precious punch line. Repeat after me, it's not about the setup- it's about the punch line...otherwise it's some sort of meandering boring poetry. Setups serve the punch line. Why? Because in standup comedy EVERYTHING serves the punch line.
Here is a short lesson in standup. Get to the point make that point funny and then repeat. Every point needs a subject, every subject needs a punch line.
Everything a comedian does on stage should serve the punch line. (see Rodney Dangerfield). His clothing, his moves, actions, reactions, facial expressions right down to catch phrases from Rodney served his punch line. In Dangerfield's case many times punch lines served other punch lines!
You get it now...serve the what???