I accept that fact, but that brings the contradiction with it. If bitcoin is an investment and not a currency, than this means the only reason it goes up is because people think that other people will buy it, and thus its price will go up, not because they want to use it as a currency.
Satoshi's intention in creating bitcoin was to make it a currency but we should adapt to everything and not be stubborn in thinking that it has to follow the original intention to be called mainstream. What Bitcoin becomes and how it is applied to life is not so important because sometimes we need to change to adapt, the important thing is that it has brought many benefits to everyone.
It has helped people reduce their dependence on third parties and have full control over their money due to its decentralized nature. It has brought financial improvement to many people and that number will continue to increase over time. That's enough to become mainstream in this world, what more could you ask for?