Free bets are not useless and they can be withdrawn. It's not easy, you need a bit of luck and sports knowledge, but it happens. I remember when FortuneJack introduced eSports on their site. They offered me a 0.001 BTC free bet on eSports to test it out. I placed a bet, won it, reinvested the winnings a few times, and managed to withdraw in the end. This was at a time when FortuneJack had a minimum withdrawal limit of 0.004 BTC.