system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do clothes and towels smell bad when they 're left to dry crumpled up, but fine when hung or dried in a dryer?
gpt
The bad smell you are referring to comes from bacteria on the towel. Those bacteria thrive and reproduce more on a wet towel, than a dry towel. The more bacteria on the towel, the more it will smell. 

So the difference is that a crumpled towel has less surface area exposed to the air, and therefore less water evaporating. Since there is more water, there is more bacteria, and hence more stank.

Edit: same goes with other clothes. The dryer a thing is, the less bacteria can thrive. Wrinkles allow moisture to stay longer.