This is nothing new, unless 10 (maybe 15 or more) years is new to you. In 2007 I did a comparison of bag size limits for US flag and European airlines. Back then the standard for most US airlines was 22 in x 14 in x 9 in. For European airlines it was 21.65 in x 15.75 in x 7.87 in (55 x 40 x 20 cm). It's just that they are now starting to enforce the size limits that have been there all along.
But the girth (2 times width plus thickness) is almost the same for both systems, so it you have a flexible bag that fits one sizer, it will probably fit both, particularly if not stuffed full. But of course, rolling bags need to be rigid (?), so you can't get a 15 in wide bag into a 14 in sizer (or a 9 in thick bag into a 8 in sizer).
At the maximum dimensions, 22 x 14 x 9, the volume is 2772 ci. Spirits free "personal item" dimensions are 16 x 14 x 12, or 2688 ci, only 3% less than the industry standard and almost twice the volume of stuff I take to Europe for 2-3 weeks. What they have done is to make it a shape that no luggage company yet makes.
As for the charge for carryon bags, this is all a ploy to collect more revenue while making the fares appear to be lower than what you will really pay. If the airlines really want people to check bags, they can speed up the time to the carousel and stop losing, delaying, and destroying bags.
Our government should make them include the cost of one bag in the fare, since that is probably what most tickets include. Then the airlines can give a discount for those people who don't have bags and charge for those with two. Do you think the discount they would give for not having a bag would be anything close to what they now charge for a bag?