Mensa: Is it a waste of human intellect?

I'm sure most of you know what Mensa is. Those who don't, Mensa is an organisation made up of extremely intellegent people with a high IQ. The the organisation is said to be the largest, oldest and well known organisation and it goals are
(1)To identify and foster human intelligence for the benefit of humanity
(2)To encourage research into the nature, characteristics and uses of intelligence
(3)To provide a stimulating enviornment for it's members

Here's my problem. We have an organisation mad eof of some of the smartest minds in the world and yet what exactly do they do. You would think that an organisation like Mensa would put their brainpower to good uses like researching a Cure for Cancer, Aids or developing othe types of cures. They discover new scientific wonders, or they could very much help mankind any different ways. But instead they rarely do anything. I mean it just seems like a waste of intelliegence and to be honest it's quite disappointing to see the lack of interest they have in other things other then themselves

Then again i may be wrong, if i'm wrong then please let me know where i went wrong. But my point is, Mensa for all it's smarts dosen't have the intelligence to put their minds together