For me, the complexity of Bitcoin is the one obstacle to achieving mass adoption. Something which I don't know if we'll ever be able to completely overcome due to the nature of Bitcoin.
Bank is also quite technical. There are so many parts such as detecting fraud, preventing race condition and initiating secure connection. But most bank customer don't know that.
Right. I agree, banks actually do serve somewhat of a purpose. I do believe they could be implemented better, and shouldn't be offering interest rates or gambling your money away. Although, I will openly admit that managing a large amount of money comes with massive amounts of responsibility. Banks have the manpower, experts, and money to be able to invest into that, and therefore provide a simple way of managing your money. When you are your bank, that changes.
Ultimately, as much as I don't like third parties managing my money, and I would prefer to do it myself. Quite simply, that is never going to be for everyone. Some people like the safety net that banks provide.
To use our money we don't need to know how it is printed, on what kind of paper and ink has been used while printing, who signed on the money, blah blah but at the end of the day we are going to use it to buy something that is what most cryptocurrency users are also doing, there is no mandatory for them to learn technical to use it in our day to day life so just learning what is needed is enough for a common user.
That's somewhat true. However, and I do believe this is one of the issues we must overcome. Bitcoin in its current state is too complex for these types of people who don't want to learn about it. The fact is; with Bitcoin you're usually in control of your keys, therefore you're responsible for them. To be able to do that you not only need to know how Bitcoin works, but you should have a decent grasp of security practices. Otherwise, you could be unknowingly be putting yourself at risk.
This is exactly why Bitcoin currently isn't for everyone, and that's okay. I don't know if we are ever going to get to the stage where it'll be simple enough. However, we've come along way with documentation, software, and hardware wallets propelled us further even further into achieving it.