At that level, it looks like it mostly happens with incumbents, especially in districts so politically polarized that the other party can't mount a realistic challenge. In these cases, the real challenge to the incumbent, if there is one, would happen at the primary level and the Wikipedia page wouldn't pick it up.

I don't know how common primary-level challenges are. I wouldn't expect them to be universal, but I did see at least one entry on that page (Ralph Hall, for Texas' fourth district) where the candidate defeated an incumbent in the primary and then went on to win the general election unopposed.