Sadly, they do know that some people will hide full or partially used bottles so they can get more and take them all home. Unfortunately, they do have to factor that in their prices.
So simple. The products are provided for your use in the cabin. Hiding a full one in your drawers/luggage so you can have extras to take home is wrong. That's why you're hiding it.
Inexpensive for Disney, of course. Do they expect that some people will do that, yes. Lots of people do it, yes. Not as dishonest as stealing other things, such as silverware, I guess there are degrees of dishonesty. A small thing in the big scheme, yes. Plenty of reasonable sounding rationalizations for getting extras to take home.
Would we take home a partially used tube instead of throwing it away? I think so, though not yet. Would we figure out some way to get extras to take home? Of course not. Disney bends over backward to treat us right, and we try our best to return the favor and mutual respect.
Awesome post!