What Happened to that really funny old movie?

I saw a bit of The Return of the Pink Panther not long ago on cable and eh, it was okay. I remember seeing it when I was 13 in the theater and I remember almost falling out of my seat from laughter, so what happened? Objectively, the movie hasn't changed: I am looking at it on a television instead of a movie screen and the print has probably faded, but for the most part the film is what it always has been.

So, why isn't it funny anymore?

Here are some possibilities:

--I am not 13 and don't have the sense of humor of a kid anymore. Objection: Most of the people at the show were adults and everybody was laughing.

--It has been 30 years since then and so the jokes are not fresh, topical or understood anymore.

--Maybe laughter is contagious. A few people enjoy the show and pretty soon everybody is laughing right along. Also, being home and relaxing on the sofa is a lot different from going-out. When you go out, you are full of energy and want to have a good time. At home, just searching through the channels for something interesting to watch, there isn't the same level of excitement.