Because the have faucet and other free coins for user through the rainbot, higher minimum withdraw is designed to avoid faucet or free coins abusers. No need to complain if you are a real player, the minimum eth withdrawal is 0.05eth which is around $10 now while for btc is 0.004btc = around $25. So you can play with eth for lower minimum withdraw. But if $10 is still too high, maybe gambling is not for you.