The real reason is that they have limited supply, and people want them. (people may not want bitcoin in the future btw) People always want gold and they want to gather as much as possible in their lifetime. It is the only solid asset which holds its true value through the centuries.
Yes because bitcoin and gold is what we need to survive. People only used bitcoin just to have gold. As I observed here everytime they earned bitcoin they are still converting it into fiat so that they can used it anywhere they want. People will keep holding bitcoin as its value continue increasing but when it dump im sure that they would going to convert it too.