Honestly those three are not bad cantrips. I can understand wanting to try some other stuff and whatnot but those are really good cantrips nonetheless. I can be happy those. And besides there weren't a ton of cantrips to choose from in the game...even in the footage of the final game. The big one that Warlock was missing access to was guidance.
I agree that guidance and thorn whip are good choices, not sure I'd ever pick vicious mockery though, but the point is that it feels unnecessarily restrictive, I can't imagine any reasonable justification to why they'd make these choices for us.