I hate to give a strange answer, but one of it's uses is to make useful compounds. Potassium is really hard to store and it is very reactive. KCl is a very needed compound by some people. It is a form of salt. There is a salt on the market called Half and half. No one with high blood pressure should have a meal without it.
I cannot find any listed use for elemental Potassium. It is just too hard to work with.