I agree. World doesn't need Bitcoin for buying a cup of coffee or for buying anything that can be bought with the credit cards maybe, but for remittances world needs Bitcoin badly. For sending quickly and much cheaper money half the way around the world, the word needs us for this as well. I gave you just two good, strong use cases.
So why adoption takes this long?
1. Bitcoin is still overly complicated, yes it is. To buy and secure your coins, you have to be very, very computer literate which most people are not.
2. People tend to change their habits very hard, especially financial habits. So this will take time, especially when we are dealing with money. People need to trust it first.
3. Directly or indirectly sabotage by our opponents. Yes, if banks came tomorrow and said to their customers, use Bitcoin, it will make our and your life much easier, of course they would boost our adoption almost instantly. Will banks ever do this openly? I don't think so. Instead they see us as a competition and they are building their own blockchains.
ad 1. Bitcoin is not complicated more that internet is. Internet was pain to use in its early years too, I remember my stressful moments when I wanted to find something and I couldn't, some services and apps changed many things.
ad 2. That is correct, but when something is clearly better people will adapt very fast, look at smartphone revolution. Or in general cellphones, they take over world very fast.
ad 3. Banks are the the enemies of bitcoin, that is obvious they won't support it ever. Instead they probably create their own Coins, like CitiBank does.