I don't take domestic flights much but just wonder how many non-elite will check the second bag

Last time I was on SJC-DEN, many people didn't even bother check in the first one and just brought those huge (more than 24" or even 26") luggage on board. The boarding process was taking so long for people to walk to the end and/or find the space.

Maybe they will if UA starts (or already starts) to enforce the size restriction