Ubisoft have about 5 engines themselves. When Microsoft acquires Acti-Blizz, they'll have close to a dozen engines under their umbrella as is, I think.

UE being picked up by a AAA studio is news, because gamers associate UE with extreme fidelity graphics. A studio using a proprietary engine is boring because it won't matter one bit for 99% of people, and is modus operandi, basically.

Edit: remembered SteamDB has a rough breakdown based on manual rules, so a lot of engines aren't picked up, but it's still interesting - https://steamdb.info/tech/

Proprietary engines tend to be more common on consoles I think - Steam has a lower barrier to entry overall, so it doesn't filter out the smaller projects as much (which are more likely to use an off-the-shelf engine).