While sitting in DEN waiting for my flight to TUL, I was able to sit with a GA and we chatted. I asked her why don't the GA enforce the carry on site limits. Its basically a time issue, so we watched a flight that was about to board for ORD, she asked me to count the amount of carry on items that are too big to bring on the aircraft. Once boarding was done, i counted 17 carry ons that were too big. She told me that it would take an extra time to listen to the .....ing from the pax about how unfair it is to have check his bag, once that was done, the GA said it would add about 15-20 to the boarding process, the GA went to the computer and told me once the plane pushed back that they had 9 gate check baggage. The flight pushed back 7 minutes late. It all comes down to on time perforamnce people.... I have said this in the past, if UA or ANY other airline is REALLY interested in this they would do something about this.