I think in part it's because they don't like firing fellow administrators and also partly that those administrators all believe in the DEI/ACE stuff (not saying they shouldn't).

I'm not sure how much it reflects market pressures and I don't particularly care if these departments exist. The truth is that one way or another universities are going to have a strategy for dealing with this set of issues. Whether that's in a stand alone office or it's mixed in with the duties of another office doesn't really concern me.