Let's say that there are 400 rooms at the resort. The accountants get together and decide that there are - at most - 4 people in a room and that, on average, they use one pool towel at day. It takes a day to launder them, so you need a two day inventory of pool towels. So you need 1,600x2 or 3,200 pool towels. And you have 4,000 on hand - because they get lost or stolen. Each of these towels represents cost to the hotel - its a tiny cost, but its a cost. Plus, the total cost of the towel is much higher - there are laundry costs involved which are actually the bulk of towel costs.
Lets say that there are 400 rooms at the hotel, and now you have 400 guests taking four extra towels each day so they don't need to pay for trash and towel. Now you need 8,000 towels at the hotel - plus the incremental costs of maintaining the extra 4,000 towels.
Since this all comes out of everyones dues, and since there is a provision for you to get towels and pay the incremental cost out of pocket instead of passing it on to other members, this is an ethical problem - basically, because you don't want to pay for your extra towels, you are making me pay for your extra towels.