but come to think of it, those little amount of money that you want to be keeping as savings why not use it and invest in BTC continuously becaus that money you want to keep as savings can also be called your (discretionary income) rather than keeping it in a bank as savings which will not bring you profit in return, why not use the money and be buying BTC and hold it for long period of time, no money is too small to be invest.
The way you said it is just too simple, do you think is everybody who believe in Bitcoin investing? We have many who believe that keeping money in the bank is better and we also have those who believe in Bitcoin investing where you hold everything in your wallet for it to grow and give you something profitable, it goes two ways. Remember that is not everyone who have that patience to wait for a very long time for your investment to come out big and before you convince people to start making Bitcoin their bank in investing I think you'd have to preach very well like you're converting a sinner to a born again before you can get at least 1 or 2 persons, it will be hard, to me is best for everyone to choose which ever way he or she wants to invest his or her money, weather in Bitcoin or bank.
You have just said it all, besides there is never going to be a time when the entire world population would invest in bitcoin, I don't see that happening. Same way we still have people who don't have a bank account. The funny thing is that, when you sweet talk people into investing in bitcoin, they won't stay for long. There are different forms of investment all over, depending on each individual risk tolerance level, they should pick which investment is appropriate for them. Bitcoin is a good investment, but it's best done when we make up our mind to do it, and not when someone is trying to make us invest in it when we are not ready. Besides we can't invest all our money in bitcoin all at once. No matter how much investment we have in bitcoin, we definitely need to have little savings in the bank as well to run our daily lives, as fiat is still the most widely accepted in most societies.