I dug up filament rolls from almost ten years ago at work. Those were on paper as well, so definitely nothing new. It's probably just becoming more common. I'm all for that, as it doesn't really have any obvious downside to storing filament on a plastic spool and it just feels much less wasteful to me.
I usually get my filament without any spool and put it on Dasfilament's little masterspool. That's even less wasteful and also cheaper.
Like you, I've got a little assortment of spools I either printed or modified for this purpose - and in different sizes - and they work great. I'm at the point of getting spoolless filament when I can and I haven't seen a downside yet.
But if I'm going to get a new spool with my filaments, I'd prefer it be cardboard.