There is no need to belive in the bitcoin itself. We can just treat it as a currency and use it a lot. Its price will rise.
You wont use something you don't believe, so if you don't need to believe in bitcoin then you would not have been using it or hoping for its price to rise, we are believing in it that its price will rise and that is what we call belief but nothing else.
we are believing because we see already the result before knowing the fluctuation will make us earn profits thats why we keep on investing
and using bitcoin its a experienced based that's why we believed.