That's been true even with TV to movie adaptations. Look at Starsky and Hutch for an example. Yes, the show had some occasional funny moments (to me, one that comes to mind is the episode where Starsky and Hutch deal with a cult assaulting their cabin to get this girl they want to sacrifice. And Hutch distracts one by popping out of a bedroom with the phone receiver saying, "Telephone!" and while the cultist was looking at the receiver, he bumps him with the body of it), but it was mostly a serious police procedural circa 1970s. Yet, for the film, it did away with the serious police procedural portion of the show and made it a full on comedy (this would be like taking Law and Order and turning it into a comedy). The same is true with The Dukes of Hazzard movie. It was a comedy that was family comedy. But for the recent film attempt, they turned it into a stoner comedy. In fact, for years, I've worried about a big screen adaptation of Knight Rider, which was an action adventure series that had it's occasional humorous moments, because I was worried they'd turn the whole film into a joke fest, moving away from what made the show what it was (this is actually no different from what happened with modern Star Trek, which they stripped away the social commentary and philosophy that the shows included with their adventures, and just made them a straight up action sci-fi film that lacks what made Star Trek what it was).