I feel the reason for the low rate of adoption is just because people think it's not for them. Bitcoin has been around for over a decade, and any thought that most people would have had about it being a scam must have faded by now.
Why would anyone believe Bitcoin is not for them if not for the lack of understanding and the FUD they hear about Bitcoin? Let's take it from this angle, you're once one of the people that didn't have an interest in BTC before, aren't you? Why don't you have an interest in it?
It is still the reason today, some are still naive about the true concept of BTC and only believe in negative things someone they trusted said about it.
But at the same time, if you look at it, Bitcoin is a risky business; if you invest money, there are two possibilities: it will either yield profits or losses.
For every great opportunity, there's always a price to pay and the price is the volatility of the market, and the risk involved can be avoided or fixed through holding till the next halving.