in the U.S. you get like .1% per year on whatever you have in your bank account. Lets say you have 100,000 USD in the bank, that is 100 dollars you make by leaving your 100,000 in the bank... Or you could buy a stock and sell it for a .2% profit in less than a matter of a day and make 200 dollars - a 10 dollar trade fee? or you could do the same thing with converting BTC/USD and whatever else, my point is that you definitely do not make yourself better off by leaving your money sitting around. Smart money makes money.