As you put this question, why would you want to keep bitcoin in a bank?
Its purpose was to do exactly the opposite, to be your own bank.
There are some tokens that say will help to make faster transactions and all other stuff, but regarding banks holding your money it is giving them back their power. They can block them, make them lost or whatever they want again and again. Like the "big" exchanges do now.
Yes, you are referring to banks for that, knowing that they are safer than these exchanges. And here comes the old story. You give them control for your assets because they have government trust and insurance in a limited amount. But again, then you are not holding your money anymore.
I see some problems for holding bitcoins or some of good altcoins in wallets because many people don't know how to use a computer, not saying to make a wallet. Tell them to make cold storage wallet and see their reactions
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Yes, here it should be a way with some certified "banks" or exchanges to have them for that kind of people or just for old people... here it will be an issue when it will go to a mass scale.
So, the big problem here is regulatory rules that will come in the near future to say that they accept it or not as legal in that country. Then, normally it should lead to have a safer way to exchange them with some trust for the big exchanges or places where it will be for buy/sell for fiat.
And also, to who said about banks, they can't disappear, at least not over night. The current system can't be changed overnight, the same as electric cars can't be made overnight as main cars because the infrastructure. Elon Musk did a lot to open the road for free electricity in "gas" stations and from what i see things are changing in a good way. Lot of countries announced that electric cars will be in big percentage in a few years. But we know them exist for last 15-20 years.
Let's hope here the trend will be quicker 5-10 years with all of the new technology that is coming.
Till then, hodl them good in offline wallet.