Well, they mostly don't. They're often using the same bedding. Most toiletries are squirt containers these days. I don't think toilet paper is that expensive. And another towel or two to wash is probably not a big deal. And to the degree the hotel has a restaurant or bar they probably come out ahead. Your hotel may take a different approach but it's near universal (perhaps outside of resorts) that hotels charge the same for 1 or 2 guests.