Bitcoin was initially created as a currency. The thing with currency is that it needs mass acceptance and that's the challenge with bitcoin. This is the reason behind bitcoin used as acommodity.
Bitcoin is made as a digital currency but unfortunitely it is difficult to apply because at this time it is in less acceptance in any companies. Althrough there is some companies accept but is not enough, that is one challenge of bitcoin. People considered bitcoin as an investment becuase it is high in terms of value.