"Reverse Osmosis Water"

What possible purpose does this sign serve? I imagine most people don't know what "Reverse Osmosis Water" is. If it's drinking water why not just say that? The only reason I can come up with for the obscure label is that people perhaps walk away wondering what it means and ultimately find out and so learn something. But when I'm getting a glass of water all I really want to know is whether it's safe to drink