The current small bottles have a seal on them. Things like the mouth wash has a piece of clear tape sealing the top. If I come across a container in the bathroom that was already open I don't use it. Again - that is why they are sealed. What keeps someone from putting something in the bottle.

Some European hotels I have stayed some time ago had dispensers but they were something you squeezed rather than pump - and in some cases they were in a sealed bag that got pierced when put in the holder rack. So not reused or refilled. Just a larger pouch than the small bottles.