So, I'll add the Carry On Hall of Shame. I'm not sure this is the best way to go about it, but it's a newspaper columnist's efforts to call attention to people who insist on taking huge pieces of luggage as carry on.
Some of the pictures on there show legitimately ridiculous and oversized luggage taken as carry ons, but one thing that I can't quite get behind is the idea that it's automatically rude and unacceptable to have a rolling suitcase and a backpack or small duffel bag.
I kind of figure that airlines can enforce the fact that only one carry on gets to go in the overhead bin, and anything you're calling your "personal item" should fit under the seat in front of you safely. But most backpacks, large purses, or small duffel bags do fit with room to spare, and some of the smaller rolling bags will even fit under the seat.
I think it's snowflakey to bring more than two bags, or bring more than one that can't
fit under the seat, or put both bags into the overhead (unless the flight is empty and there's lots of space, but that almost never happens these days). But just having two bags as large as the airline allows is not by itself rude.
I end up bringing a rolling suitcase (not small, but not the largest size allowed) and a tote-bag-as-purse most of the time, just because I no longer trust airlines not to delay my bags, take things out of them, or keep them dry after a variety of experiences. I therefore keep everything I truly care about with me, along with stuff to do on the flight and a change of at least underwear/socks/shirt and my pajamas in case my bag is delayed. That typically fills my two bags completely full. However, my rolling suitcase fits easily in all overheads that fit any rolling suitcases (and I gate check it on planes too small to accommodate them), and I keep my tote bag under the seat, along with my coat if I have one with me.