The better you get at carving, the more you realize how important it is to be able to carve "from the ground up". This means changing edges starting with your toes, then ankles, then knees, then hips, etc. This is opposed to the practice of making big upper body movements and arm gesticulations. Carving this way allows you to be more dynamic and fluid, and it improves your ability to maintain and recover balance.
The higher your binding angles, the less leverage you have across the board with your ankles, therefore you can't use them as well for the advantages stated above. (On a Skwal, you have zero ankle leverage.)
I still love my Madd 158 (a hair under 18cm wide) but I'd probably like it better if it was 20cm. I've realized I like riding with binding angles of around 57-60 degrees.
I'm absolutely loving my Coiler Schtubby 170, 21cm wide. It feels like a snowboard again.
Wide boards actually never went away. Factory Primes and Speeds came in 20, 21cm widths until the end. People just started trying skinny boards and got hooked on the hyper quick edge changes for a while. Also, skinny boards and higher binding angles make it easier to stop the dreaded "toilet sit" technique problem. I think skinny boards helped a lot of people get over a hump in their technique progression, and now they're finding they can return to wider boards without returning to old habits.
It's all an evolution. Kind of like how boards went from sym to asym, back to sym.