These days, every show seems to have the "average man/woman" character, the one whose sole purpose is to balance out all the craziness carried out by the other characters in each episode. Oftentimes, though, this person can come across as so insanely dull or annoying that the show would probably be better off without them.
People often point to Skyler from Breaking Bad as a prime example, as she comes across as a total downer, even if her true motivations are to keep her family safe and intact. There's also a case to be made for a character who replaces another beloved cast member, and just can't quite live up to people's expectations (something that happens far too often).
It's hard to provide enough background and intrigue to individual characters, especially when they're generally seen as a single piece of an ensemble. For whatever reason, these characters became a nuisance to the audience, and are seen as inconsequential additions to already full and endearing casts. This has nothing to do with their individual behavior, but instead focuses on the fact they offer nothing of real value to the show as a whole.
Vote up the characters you wish were excluded from your favorite programs, and vote down those you believe were irreplaceable.