Why do people find stuff hilarious so easily these days?

I am trying to understand how people can find amusement at this new "brand" of comedy, I'm not really sure how to describe it, but it's just about elaborating things. Seth MacFarlane is probably the biggest culprit I can think of. Lines like "I look like something you give to your kid when you tell him grandma died" or saying out a sequence of different "trashy" girl names. Others, like the trailer for The Interview, makes a joke of Michael Phelps swimming from NK to Japan, and dancing to a Katy Perry song with Kim Jong Un. It really takes ZERO effort to come up with those stuff because they are simply different words or situations put together, they serve no purpose not even hilarity.

For example, here is something I would consider genuinely funny:
http://vimeo.com/34178476

There is progression in the humour, and there is a level of depth in the characters' reactions, especially the brilliant Steve Carell who switches from frustration to child-like intrigue to joy.

Or this:
https://www.youtube.com/watch?v=qVl3J5L0d98

A hilarious take on horror movie cliches that is genuinely absurd, coupled with great physical humour.

But the fact that The Big Bang Theory is thriving and movies like Ted make millions mean I rarely see scenes like the above today. What's the point? They just have to put together random thoughts and people show up.

If anyone here laughed at the grandma died joke, which is supposedly one of the best jokes in the movie since it made it to the trailer, I'd like to know why. I won't insult you or anything, I'm just curious if you ever felt "y'know, that kinda wasn't funny at all".