This is a little out there, but maybe - what if - not all robots are compatible with all alliances? It's crazy, I know, to think that some teams would choose specific robots because they fit with their strategies, but it could happen.

Sarcasm aside, regardless of what the pickers' intentions are (provided the pickers know what they're doing), no team is chosen at random. Every team is chosen for a reason to play a specific role on an alliance. Now if a team is chosen with an intended role in mind, their alliance partners can help them better perform in this role, and the team is willing to improve their play to better contribute to the alliance, I see no reason why those partners shouldn't be allowed to help the team.

I know why this decision was made, and while I wouldn't break the rule if they enforced it, to paraphrase Nick Fury from The Avengers: "I recognize that the Q&A has made a decision, but given that it's a stupid decision, I've elected to ignore it."