If you really want the reason why bitcoin was invented then you should watch videos at you tube talking about how bitcoin and why it is created. But I will cite some special reasons why it is created. One of the reasons why it is created is because the society is already fed up with the unfair banking system practices and it wanted to revolutionize financial technology. It wants to banked the unbanked and let your wallet be your own bank. Unlike the banking system bitcoin is created without a center.