Only one factoe scares me from investing into bitcoin and that is the coins, ico, tokens, cash that are new in the system and has a great mission that will soon maybe one of the greatest enemy of bitcoin in terms of number of users and price.
One factor that people are scared to invest is that it is unstable due to the fact that people see it as an asset than a currency. Other factors is that it is risky due to that you will never know whether you invest in a legit ico or you've been scammed no matter how much you research that ICO. Also if you don't have any information on the crypto you want to invest.