Question for through hikers...

Generally, when I've backpacked, I've completed only short trips of a week or less. When I get back into town, I have easy access to toiletries (shampoo, soap, a towel, etc.) since I'm back at my car.

On a through hike, do you end up purchasing these items at each town stop? I would hate to carry a whole bottle of shampoo, or a full bar of soap, or a bath towel, on the trail.

Probably sounds like a crazy question, but I was just wondering how you handle this...

Thanks.