Yes, anchoring, obviously.

The mechanism that seems most important to me doesn't really involve any sort of cognitive bias much. It goes like this. You are on (say) $50k/year. You are good enough that you'd be good value at $150/year, but you'd be willing to move if offered $60k/year, if that were all you could get. You apply for a new job and have to disclose your current salary to every prospective employer. So you get offers in (say) the $60k-80k range because everyone knows, or at least guesses, that that's enough to tempt you and that no one else will be offering much more. You might get a lot more if you successfully start a bidding war, but otherwise you're going to end up paid way less than you could be.

Note that everyone in this scenario acts rationally, arguably at least. Your prospective employer offers you (say) $75k. This would be irrational if you'd turn that down but accept a higher offer. But actually you'll take it. This would be irrational if you could get more elsewhere. But actually you can't because no one else will offer you much more than your current salary.

(You could try telling them that you have a strict policy of not taking offers that are way below what you think you're worth, in the hope that it'll stop them thinking you'd accept an offer of $75k. But you might not like the inference they'd draw from that and your current salary.)

Obvious note: Of course people care about lots of other things besides money, your value to one employer isn't the same as your value to another, etc. This has only limited effect on the considerations above.