Wow. Your sense of smell must not work very well. I bet that towel smells like a wet dog on day four, and reeks like low tide by week 2. I would ask someone "does this smell sour to you" and see what they say.
I round up all the towels 2 or 3 a week, sometime more often if I suspect anything icky has been going on or if anyone is the family is sick. Sick people get a new towel every day. All handtowels and washcloths are changed out daily.
I only use towels that will stand up to bleach and hot water, too. Anything that doesn't isn't in my house.
I have a family of 5 and do laundry every single day. Anyone that thinks washing a towel is a waste of water and detergent probably doesn't own their own washer/dryer or is used to living in filth. Sorry, that's just nasty.
You should read the book, "The secret life of germs" and then re-evaluate your views on cleanliness. I have a doctor of infectious diseases in my family, she's an M.D. with a PhD-- it's my mother. She would gag if I told her about your 2-3 weeks on a towel. Dear lordie if that's how you deal with towels, what's going on in your fridge?
Just so you know, every time you flush your toilet you are spraying a bit of what's in the bowl onto everything in the bathroom. Close the lid before you flush. For pete's sake clean that bathroom, too. Change your towels every 3 days max and wash them in bleach, good detergent with hot water.
Now I have to go scrub my skin with a wire brush and gasoline. Ew!!!!