You should note that the number 7 can be rolled with the most dice combinations, which is why the casinos use 7 as the "craps roll".
Please review the roll combination table below:
Total Odds Combinations
2 35-1 1 + 1
3 17-1 1 + 2, 2 + 1
4 11-1 1 + 3, 3 + 1, 2 + 2
5 8-1 1 + 4, 4 + 1, 2 + 3, 3 + 2
6 6.2-1 1 + 5, 5 + 1, 2 + 4, 4 + 2, 3 + 3
7 5-1 1 + 6, 6 + 1, 2 + 5, 5 + 2, 3 + 4, 4 + 3
8 6.2-1 2 + 6, 6 + 2, 3 + 5, 5 + 3, 4 + 4
9 8-1 3 + 6, 6 + 3, 4 + 5, 5 + 4,
10 11-1 4 + 6, 6 + 4, 5 + 5
11 17-1 5 + 6, 6 + 5
12 35-1 6 + 6
As you can see, there are far more combinations of the dice that will total a 7 than will total a 2. Therefore, the odds against rolling a 2 are much higher (less likely) than that of rolling a 7. The frequency of these numbers being rolled is the foundation on which the game of craps is based.