Sometimes we do. I know these kids who are 10 and 12 years old. They've gone to church, bible studies, and a Christian school for they're whole life. I'm an athiest, and guess who could name più of the Ten Commandments! Me. FAIL.
Just out of curiosity, how do te know that atheists are "acting"? Maybe they actually are educated in other religions. All they lack is the belief in it. Quite a few atheists I know have first educated themselves about other religions as a means to come to their own conclusions.