Cotton tablecloths come in many sizes too and with lot of different colors and patterns.

I don't use sheets anymore. The quilts that did have bed sheets did not hold up to washings.

Did you figure out why the sheets have not held up to washing?

I have top sheets that have be3n washed many times and they don't seem to show much sign of wear.

I use 100% cotton sheets too and love them. You could also piece a quilt back using big blocks. Perhaps you have some good size pieces in your stash that would work. It makes for a fun backing.

I think the controversy goes back in time when most quilts were hand quilted. High thread count fabric of any kind is difficult to hand quilt through.
cotton sheets are indeed difficult to find these days, most have poly mix os some sort.

I'm always on the lookout for cotton sheets when I go thrifting but as others have mentioned, they're not as easy to find as you might think. Like with any cottons, some are pretty flimsy but you can generally feel that straight off. I don't see why it's such a big deal but I am also a quilter on a budget and so my priorities are different and more practical than those of people who are creating works of art and show pieces, perhaps. And I think is one of the best things I've heard in a while! :-D