It isn't supposed to be funny.
I've been on several WN flights, and all of the cabin safety announcements have contained the required elements (seat belts, oxygen masks, exits, routes to exits, including floor lighting, seat backs, tray tables, safety card...not necessarily in that order), but some flight attendants fancy themselves comedians and make it a stand up act. (WN aren't the only offenders here)
Yah, yah, I've heard the blather about it being a way to get people to pay attention, but frankly, I think it also conveys a level of contempt for the procedures. (Or maybe its just because I fly too much and have heard their stupid jokes over and over and over and over again). If they're there for my safety, I wish they'd convey that they take the job seriously as well. I don't doubt they do, but they have a funny way of showing it.
I've been on some flights where the pointy end makes an announcement that we will be provided important safety information by the cabin crew, so pay attention. Didn't note if that helps or not.
...I'll confess to sometimes not listening...usually when someone's being silly about it. Then I tune them out, review the card, look for the exit, count the rows and wait for the stale jokes to end.