You just confirmed what I've been suspecting for these last several years. They're blending in synthetics to keep their costs low and their profits up.
I mean, I can't even get all-cotton socks any more. It so annoys me to see "Organic cotton" in large letters on the front of the sock packaging and then see that it's only maybe 60% cotton. The rest is spandex or some other artificial fiber (in the tiniest print hidden on the back). Not that I require organic cotton, but when you see that and have to pay the higher price for it, you expect the item to be pure cotton.
Seems to me it doesn't really cost all that much more to use cotton and sew in some durability. Maybe this is an opportunity for someone who wants to start a business. Without having millions of stockholders to satisfy, the profit goal could just be earning a decent living for the people who work there.