There’s sometimes psychological reasons people tell stories badly. One element of good storying is being emotionally connected to the words you’re saying, but if people are in denial about something, or suppressing the emotions involved, the story can sound somehow flat and affectless.
Resonated with me about how jokes start to slowly die once they get codified. As soon as the words are locked in, I can feel the juice slip out of a bit and crowds slowly start to detect that and then you're back to a bit that doesn't work. For me, constantly tweaking or trying new tags is one solution to staying connected to the bit. Another is to just change the words. Keeps from going into that autopilot mode. Also, putting it on hiatus for a bit can help rejuvenate it later.