Three thoughts:
UA needs to get baggage handling down better. Even at a small outstation I can be waiting 20+ min for bags.
If crew want to bring 3+ bags, they should go in the back. I've never seen a crew member at a baggage claim and at some point they are ending their trip and could check.
No airline wants to be too harsh on carry ons because unless the others follow they'll get tagged as "flyer unfriendly".