Well, of course I can believe the mold that grows on them! That’s why I wash them periodically. Even the cheap plastic ones can be washed. You use soap, baking soda, Lysol and throw a couple of towels in to scrub it. Viola. Clean. I only replace them if I find a shower curtain I like better, so….three times in the last 15 years. I have seen the COOLEST shower curtians that people make by putting in a cheap, plastic curtain on the inside, and a really nice actual drape, like a window drape, on the side facing out. My daughter has that.