See e.g. Georgia's election to Congress in 2014 -- seven out of 14 Congressmen ran (and won) unopposed. Or Massachusetts -- six out of nine unopposed.
There are also hereditary fiefdoms -- e.g. Newark, NJ.
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.
Some of us enjoy being sidekicks.
Some of us would like to meet sidekicks in potential, see how the interaction goes, and have sidekicks.
Last time I tried posting about sidekick matchmaking here, it turned out to be very valuable for me, but not for many people (I think only two pairs of sidekick were created as a result). Now, once again I'd like to find someone who enjoys that role to help me out with many projects.
I'm looking for suggestions on how to get people together to do that. For the time being, if someone needs a sidekick or wants to be one, post about it in the comment section. I'd love to see a permanent solution for this information spreading problem.
My experience with Sidekicks
I'm not sure what Anna and Nick thought of their sidekicks, but my experience was undeniably positive. Having a sidekick was motivating, saved me great time, and, most importantly, felt like I got a surge of muscle strength specifically in the types of tasks I'm particularly inept at.
By contrast, my experience with people hired to help was mixed (virtual assistants) or negative (personal assistant).
Use the comment section to either offer or request sidekicks, explaining a little more about you and what you'd like this partnership to mean