I don't think cotton is all that big problem.

I work full time in my very own blacksmith shop. I play with fire alla time, and get burned regularly, on my arms, legs, face, etc..

I have several shop kilts made from cotton, and several made from wool. Both have had hot mill scale, hot grinding sparks, and liquid molten borax welding flux at about 2400f bounced off 'em. I can't see a hell of a lot of difference. Granted, the wool is a little less flammable, but it's not like you go up in a ball o fire wearing cotton, even if it is subject to some pretty intense heat, though I do make a point to not stand directly in the flame of the gas forge.

Wool is king, for many reasons, but cotton is not a sin, nor is it more dangerous in most (nearly all) situations. Synthetics, OTOH, just simply do NOT work in the shop, as kilts, shirts, pants, or much of anything else. But then that's a personal rant, and not really relative here.