Some people think pointing out the obvious is a conspicuous, transparent and plain way to make people laugh. But I think observations are not as easy as they look.

You actually have to pay attention to something to say "Have you ever noticed _____", and you have to a grasp of bargaining to say "What's the deal with ____". These sort of things aren't easily picked up upon (I'm not sure if you've noticed that or not).

As you can see observations are plainly noticeable for anyone aside from the blind. But even the blind pick up on things as long as they are within their reach. Otherwise you have to hand it to them.

One last thing about observational humour: have you ever noticed that a lot of observational comics ask open-ended rhetorical questions?