I think the main thing preventing adoption is that people are set in their ways and Bitcoin is new and scary.  A lot of people don't want the responsibility of having to safeguard their own coins, or even learn about the process.  They've heard horror stories about keeping funds on an exchange and don't trust themselves to store it themselves, so what are they to do?  Many people like this would likely only get exposure to Bitcoin through things like ETFs in their retirement accounts.  Over the years I've given friends quite a bit of BTC and it almost never fails that they lose their keys or some other thing that caused them to lose their Bitcoin.  The average person is definitely not ready to have their finances in their own hands...  There are still folks paying financial advisors to set their money in index funds...  People have a long way to go when it comes to financial knowledge and I don't see schools doing their part.  For this reason, I think it would realistically take generations before everyone got on board with cryptocurrencies.