Speed of the transaction in Bitcoin can be enhanced by upgrading. You forgot to mention that you need days if you are going to transact in a bank for a certain amount and it can even freeze your account.
I know they can freeze my acount and as you say, some transactions take days, but at end the number of transactions they do are massive and not comparable with bitcoin.
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Yes, for me this is the biggest obstacle for bitcoin to become a global currency, transaction speed.
Unless the blocktime of bitcoin reduced, i think peoples will prefer to use another crypto to pay something faster.
There are two solutiosn, the first one is like you say, blocktime reduction, that would provide more transactions confirmed in the same period of time, the other way is bigger blocks, this way we could have more transactionsin one block. But at end the solution is to mix this two options, bigger and faster blocks, but again, that will end in a huge blockchain and not sure if we want that.