On Hotel promises

The sign in my bathroom here in Austin tells me that if I want to reuse my towel and save humanity from excess water usage, that I should hang it up on a rack, but if I want my towel laundered, I should put it on the floor.

I put two washcloths on the floor, but hung up my handtowel and bathtowel, prepared to use them again. Tonight, I find that all my towels have been replaced with fresh ones, including the ones I tried to keep and use again.

So, why do hotels hang these signs up if they don't intend for their staff to actually follow those instructions? It reminds me of the infamous email forward (and probable urban legend) about the guy who wound up with 8245682741 mini-bars of soap instead of his 1 full-size bar.

I'll try again tomorrow, but don't expect to be able to keep any of my towels then, either.

Update: The next day (that is today, Wed), I hung my bathmat on the shower curtain rod and my bath towel on the towel rack. Once again, all towels were replaced with fresh ones. In the grand scheme of things, this is a pretty minor point, but it just seems so ridiculous to me when hotels put out these signs suggesting that they are environmentally conscious and want to save water and detergent and then don't follow through.