According to me the unstablity in the market value is the main reason due to which many people are not investing in bitcoin.Sudden drop in price and moreover no surety that when will the market value increase adversely affect the number of investors of bitcoin. Moreover their is no control on the transactions as their is not central body to control it which also create a sort if fear in the mind of investors .
As I think that there are many different types of factors leading to scarcity of investing. I want to mention to the lack of knowledge foremost. Because you know when one doesnt have much knowledge about cryptocurrency, he is probably affected by lots of bad news about this field, he cant control his mind of that bad news. Besides, when one does not understand much about crypto, he maybe get fruitless. Next, the patience also plays an important element. Investing is not a difficult job in crypto, but it requires the patience. If one is lack of patience, he will be in loss quickly and then getting fear of loss and getting away from it. In short, a man whos afraid of investing relying on many factors.