Is it entirely because of the money that can be gained from the potential price increases, or is it because you believe in the tech? Maybe you do not believe in the BTC but other cryptos, that counts as well for 'believing in the tech'.
If you do not know whether you believe in it or not, you have not read enough about it, and then you are in because of potential gains.
I personally do not care at all about the reason, and there is not one of the two which are morally 'best'. It is completely okay to invest from the only belief and hope, that the money invested will become more worth. I just think it is fun to see
I certainly believe that people invest in bitcoin solely because of potential gain. It is considered as business to some people due to its high demand on the market and being the first successful cryptocurrency to ever exist. Maybe right now many digital currency exist but none is capable of surpassing bitcoin in terms of volume and reliability.