On a recent FLL - YUL flight, I had this occur. Had a single hard sided case as my carry-on. Placed it in the bin above after boarding early. Pax rolls on with three personal items + duty free. Asks FA for "help" in finding space. The FA asked, holding my case, "who's is this?". I reply, and she asks if I would mind keeping it at my feet. I said yes, but pointing to the hog, "he can keep it at his feet". Funny, that didn't appeal to the hog who then kept one of his bags + duty free at his feet. He still had a rollaboard and soft bag taking up bin space though.
Seriously, we're a privileged bunch to travel. But my point of view is that if the airlines don't patrol and enforce the cabin luggage policies, don't look to those who abide by the rules to be put out of a comfortable flight by those who abuse the rules. Full stop.