There's a law called "the Weak Law of Large Numbers" that basically says that the probability of some event reflects the number of times you'll see it if you have enough goes. The point then is that if you roll two dice often enough and note how many times you get a double six, you'll see whether it occurs (roughly) once every 36 rolls or (roughly) once every 12. You will get the first result, or at least something close to it, so that the layman's thinking is flawed.
At the very least, that's because there certainly aren't 11 possible results: 7 can occur as 1+6, 2+5 or 3+4; 6 as 1+5, 2+4, 3+3; and so on -- tallying all those up gives you 19 distinct sums, some of which give the same total, so that at the very least you should expect odds of 18 to 1 against a double six rather than 11 to 1. And then finally, some of these sums can occur in multiple ways: 1+6 and 6+1 are also distinct from each other. This is true whenever the two dice show different numbers, which does indeed mean that there are 36 different results that are possible -- of which only one is a double six. Hence, 35 to 1 against assuming fair dice.