Think how much worse it would be if you had to see the movie. Usually the trailers for comedies contain funny stuff — sometimes the only funny stuff in the movie. In the case of the new Pink Panther, they either couldn't find one funny moment to include, or they opted for a bold strategy of showing really bad stuff so that people would be pleasantly surprised if they went to see it anyway.
One of the things that made Peter Sellers so funny was that his silly French accent had some connection to reality. And the writers provided words that really worked with it. Steve Martin trying to say "hamburger" with whatever that accent was supposed to be was just patheticly bad.