My guess is that they need them because they 1) need something strong enough to carry some weight. The cotton part is ok. Its also surprisingly thin, and personally I really like the feel of it. Stone came off before I even wore it. I only hope the company gets this review and can send better instructions. My last pair of Sanuks lasted 3 or 4 years, so Im holding on hope that the next pair is better. Does not look or feel cheap and is able to support a reasonable number of clothes. Never noticed a smell and no one in our house really has a foot odor problem. Surprising, but I like the idea they can be improved through updates. I looked through the internet to get a cheap alternative and oh boy this is a serious improvement.