Hope you find your cotton bottoms, but just to set the record straight, Modal and Tencel are actually 50% more absorptive than cotton, much smoother to the touch (think silk instead of cotton) and able to maintain their softness through multiple wash cycles since soap residue doesn't stick to the fibre's ultra smooth surface. The ultra smooth surface of the fibre also prevents bacterial buildup much better than cotton. These anti-microbial, ultra-absorptive properties, along with the lightweight softness, are why Modal and Tencel have become so popular for technical gear and underwear. People who have sensitive skin often find Modal and Tencel much easier to wear than cotton.
In addition, there are also many who consider the newer manufacturing techniques make Modal and Tencel a more environmentally friendly choice than regular cotton, which uses some rather nasty pesticides. Organic cotton is good, but it does come at a higher price point.
Of course, sleepwear is a very personal choice, but I don't think it's right to lump Modal and Tencel in with synthetics like polyester and nylon. Its properties are quite different
