But why we need banks to store our crypto currencies?

Actually this is against the crypto currencies,because the main reason of crypto currency invention is making transaction without without any third party help.But now they are banks involving here so they want to control our money that is what they are doing for centuries now they are coming to the crypto currencies too.
We can store our crypto currencies safely without anyone's help and we just have to store our private keys safely.So people don't want any banks to store our crypto currencies.
I agree with you i think we dont realy need a bank just to hold our money and when the times that we badly needed our money it takes a long time to withdraw our own money just like today when the banks holding our money. If the banks holding our money they are always asking us a lot of requirements. Thats a big hussle for us we are the owner of that money and we freely use our own money. Unlike crypto currency we have our own wallet just like a bank and we can freely use our money any time that we like.