I think many people need to hold in bitcoin because they need to survive they daily life, they need to buy things they need. So they still trusting bitcoin for they daily life. 
There's a lot of reasons why people hold their Bitcoin, and one main reason is to wait for the right time that the Bitcoin has a higher sell exchange, to make a lot of profit from their investments on let's say, a person bought a lot of Bitcoin from the last dump. So that is pretty much the reason.