Why is so it hard to find 100% cotton tops on Gap website?

[ChickenVindaloo]

I'm stocking up on long-sleeved t-shirts but most from Gap seem to be a mix of cotton and other materials eg "modal"

M&S do 100% cotton but they aren't as thick as I'd like.

Am I missing something?!

Thanks

Maybe gap don't sell them?

It's just you would think cotton tops would be Gap's bread and butter!