Leeches are cool little critters and actually help with a lot of blood conditions. They're great for dealing with swelling and even things like varicose veins.

Their saliva/secretions are indeed used as the basis for some medications to treat blood-clots, though we don't necessarily use the leech itself much in those solutions.

Way cooler than land lords. Also a leech will detach when it's full. Land lords will just keep going.