The trouble is it's pure chance so if you have won twice in a row and a small DC is getting upset it is very hard to cheat to let them win.
Scenario: you need 4 to win.
You: < throws dice > What have I got? Four? Whoops dropped it. Silly Mummy, better throw again.
DC: You don't have to, Mummy.
You: No no no, that's OK, need to be fair
DC: But you didn't make me throw again when I . . .
You: Well I'll just throw again shall I? < throws dice >
DC: You got FOUR!
You: Oh! < weak smile > Now, lets see, < moves counter furtively > One, Two, Threefour. Oh still one to go.
DC: Mummeeeeee! You didn't do it properly. Go back and do it properly.
You: Oh...kay... One, Two, Three, Four. Oh I've won again.
DC: Waaaaaaaaah!!!! I NEVER win!!! I'm rubbish at this.
You: DC darling, I keep telling you it's just luck, there's no such thing as good or bad at this game.
DC: I hate this stupid game < throws board on floor, storms off in tears >
Whereas things like Monopoly are a bit easier to let them win (only once in a while, mind) "Ah no, I am a bit bored with having Park Lane AND Mayfair, don't think I'll bother this time."