I completely agree with lost_in_translation, I have never understood why hotels used bars of soap instead of liquid soap unless it's because bars of soap are cheaper... they seem so wasteful when most stays are very short and they're less pleasant to use. I would love to see more hotels use liquid soap. If I had to guess, bars of soap are cheaper when compared to the cost of replacing stolen liquid soap because many guests have sticky fingers, but with the locking mechanisms many hotels have for shampoo/conditioner/shower gel, it seems plausible that the same mechanism could be introduced for hand soap.

I recall seeing something about how there's some efforts in the U.S. to recycle unused hotel soaps into new soap because of how incredibly wasteful hotel soaps are, Clean the World claim to have recycled hundreds of millions of soaps so I guess they're the organisation I've seen before, maybe it was this video: