I use a plastic soap dish to hold the soap (something carried over from my military days) and they always leave that alone. If I used the bar of soap, they will leave another one, but usually don't leave an extra one every day. Might be something to think about if, like me, you see no reason to not use the same bar of soap until gone. BTW - I wipe it off and carry it in my shaving kit, I have never had a problem as far as water getting over things.

Just a thought - do the hotels use any type of a cleaning solution for the tubs? If so, maybe when they overspray the soap they throw it away, and some housekeepers would rather not have any question about if the soap had some type of harsh cleanser on it, so they automatically throw it away every day.