It doesn't take three days to clear. It takes three days for them to use your money to their advantage before they give it back to you.

It reminds me of sports betting websites. They'll take your credit card (or whatever form of payment) and instantly let you gamble with it. Ask for a cashout and it takes them 5-7 days to process the transaction. Meanwhile you can cancel all the way up to the 7th day and gamble it away! Such a racket. (That I would constantly enjoy if it were allowed)