That's not conditioning. Everyone pretty much always follows in there parents footsteps.
Because they are indoctrinated into the religion at an early age and taught that it is the right way of doing things. If there was no conditioning and no indoctrination then you would let the child learn about lots of religions and then make an informed choice when they are old enough. This isn't what happens. Generally Catholics bring up little Catholics, Muslims bring up little Muslims, Methodists bring up little Methodists. All of them passing on their own indoctrination to their offspring.
The same thing tends to happen in the country to a lesser extent with political views too, I know a couple of friends whose answer to "Why do you vote Labour?" was "Because my parents vote Labour" with no real thought behind it.