Bitcoin is a virtual money and they cannot touch it, so some people thing is is not real.
Also people who have bitcoin likes to keeo it rather than spend it like fiat.
I don't think that's the reason why they don't want to use it. Bitcoin being a virtual currency is something that needs deeper understanding so that you can appreciate it. Not just because you can't see it, you wouldn't believe it already. Lots of people are fond of religion wherein most of the things are not visible yet they believe. Bitcoin is really way better to be kept than spent though most specially when its value is rising.
There is no need to bring religion into discussions like this and that reason is not very appropriate for the future of bitcoin itself. If you are aware of an adoption, then that is the answer, because with the adoption at least there will be many users can have other interests to use bitcoin as a means of payment and other transactions, if you only use bitcoin as an asset without a good increase in many factors and other elements, then how can bitcoin have a good future.