Why does it take so many days to transfer money between two banks in the US. I have accounts with two different banks in the USA, and whenever I transfer money online between those two banks, it takes around 3-4 days.

The thing is that when I transfer money, it is debited from my source account instantly. But it takes 3-4 working days, for it to reach the destination bank. So in the interim period, who has the money?