I wouldn't be at all surprised if a nsignificant number of investors regularly bet their small investment gains on high-odds bets.  If they lose their capital is still untouched and if they win they get some nice winnings.  If someone leaves 10 BTC there and gets 0.1 BTC interest are they going to take out 0.1 BTC or have 100 'free' spins at trying to win 1k BTC?  I reckon quite a few will do the latter.