Just Here For The Funny

Squidward: Patrick, what are you doing here?
Patrick: Uhh.. I don't know. (smiles) I'm funny.

When some viewers, readers or listeners like a work for the plot... there are twice as many there only for the comedy relief. This trope covers any type of medium, even if the fandom itself isn't known for its comedy.

More likely to pop up in children's shows than anything else. Periphery Demographic comes up often into play. If the show is mostly targeted towards pre-teens, then it will garner a healthy amount of plot. Of course, you need humor to keep it running. Then that's when it all falls apart.

The plot plays a bigger part later in the show. Less humor, less humor addicts or young children who don't 'get' it watching it. Ratings fall. Ratings Stunt, perhaps. Perfectly decent show gets canceled.

Could also be when a humorous show hogs the ratings of a certain television channel... making other shows' ratings fall.