The original idea was to take back control of our money from greedy and corrupt banks and politicians. Very very very few people use it as that now though. Most just see it as a get rich quick scheme.
As we are in the privacy sublemmy: All of the privacy issues have already been solved, those that keep saying that it is a log of everyone you ever paid kept forever have no idea what they are talking about. Just simple thing like that you should (almost) never use an address twice removes a lot of the privacy concerns. There are also other ways to obfuscate and stay anonymous.