You're right concerning the risk. But because of there are no odds given there are some fantasy odds you don't get anywhere else. In Case of the champions LEague outcome there is a bank of 0.18 btc now and the odds for Juventus to win are 2.4 ... so you can bet 0.025 BTC without really affecting the odds and everywhere else it's around 2.0...
And The Fact you can bet from your private wallet is nice because you got the winnings directly back in your private wallet no withdrawal waiting - no verification...