People look at bitcoin and see money that can be sent anywhere without needing approval from anyone. They can store their money themselves. They can program their money. They know the supply of their money can’t discretely change underneath them.
Some people are opting to change their dollars to btc. Some are opting to hedge a small amount into this new system in case recent monetary experiments explode. Some people are speculating (as they do in forex markets today).
Just because more people want to explore this brave new world doesn’t mean it’s a bubble.