There can be 1 bitcoin split up into trillions of pieces. 21 million means nothing.
Let's pretend that there is one piece of gold on Earth and it's the only form of currency. This currency will be needed for countless transactions. Scientists find ways to slice the single piece of gold into increasingly small pieces to buy or sell an increasing number of things. Eventually paper notes are issued on the promise of the actual gold for those who are willing to store their microns of gold in a depository or bank.
BTC is no different. Banks can turn BTC into fiat as long as there are people willing to store it there. They can offer a higher return for those willing to store it there for longer terms.
I don't understand why so few people seem to be able (or willing) to figure this out.
The difference is that the old justification to store gold in banks is not longer there anymore, in the past people stored their money in a bank because it was safer but now a bank is more insecure than if you store your own bitcoin so while they may try, many people are not going to let deceive themselves and store their bitcoin in a bitcoin bank.
I'd like to add that people can't create more bitcoin to lower its value. The dollar and other currencies can be printed making a larger supply. This in return makes your supply less in comparison.
So if you hold 1 Bitcoin. Your amount in comparison to the total supply is 1/21,000,000. 7 years from now, if you never touch it, your comparison is still 1/21,000,000. If you have $10,000 and the total is $5,000,000,000,000. Your comparison is 1/500,000,000. 7 years from now, you still have $10,000. However the total supply may increase to $10,000,000,000,000. Your comparison is now 1/1,000,000,000. So basically the value of your money has halved itself. With Bitcoin, this doesn't happen.
