Haven’t there always been rules about only 1 piece of carry-on, and there were limits for its size? It was simply never checked. Resulting in overhead boxes being full because some people brought multiple bags, resulting in some people being unable to store their stuff overhead. They’re just enforcing the rules now right? Or has something actually changed?
Personally a great fan of the CGP Grey videos. Continents in this case: https://m.youtube.com/watch?v=3uBcq1x7P34