#1 Reason: Crypto gets a lot of bad publicity. Almost every time I see a headline about cryptocurrency, it's either "XXX million dollars in BTC stolen in hack!!!" or "BTC has crashed again, losing XXX billion from market cap!". All the bad publicity makes them afraid that they'll lose their investment.

I would say that's the main reason, although there are others. There's always the fear of the unknown, and people who don't understand how crypto works naturally doubt its security and value. There's also the difficulty of explaining how it actually has value, since it is an intangible, digital asset that has no real-world backing or organization behind it.