Just throwing it out there, I like companions.
If you're warping your deck enough to make the companion available, your deck probably sucks. And don't get me wrong, a lot of my decks suck. I have no issue with decks that suck.
The point is that in order to get a companion you have to warp your deck massively and you only get the benefit once. There isn't a single companion card that I wouldn't rather have in the command zone so I can repeatedly get their benefits, and if I'm doing that, I don't have to care about the stupid clauses.
Take Keruga. That effect is strong. That's a lot of card draw. It's not worth not running
Sol Ring and
Counterspell and
Rampant Growth and the talisman and signet and all that good stuff for, especially when once it's dead, it's dead. Same for Obosh, Umori, even Jegantha. Every single one is better in the command zone and not worth messing your deck up for. The only one that would have been good is Lutri, so the ban makes sense to me.
Companions are only good for idiots like me who like stupid rules and shit decks. No one looking to make a good deck is going to consider bastardising their deck that much for it, so I'm all for letting idiots like me have their fun and letting the good players ignore the mechanic entirely.