It really depends on which hotel/motel you’re staying at.
At motels, and cheaper hotels, the hotel towels will be thinner. At pricier hotels, the hotel towels will be thicker.
The answer is actually twofold.
1.) Thicker towels are obviously more luxurious to use.
2.) Thicker towels last longer. Since hotels wash the towels almost daily, they need towels that will sustain the abuse, and last for a reasonably long time (a year, if not longer).
One of the ways in which to make towels last longer is to make them more absorbent to begin with. The more towels you need to use to dry off, the more towels they have to wash.
To make towels more absorbent, they use long-staple cotton – which does not get ring-spun like the cotton in cheaper towels.
“Un-twisted” cotton, has a looser weave, which creates more space between the individual fibers – making it feel thicker.