Like I said earlier, most people are born into it. You say it's a "choice" but not really in most cases.
You think the average Muslim could just quit Islam if they wanted to? No way. They would at the very least be disowned by their family and friends, and quite possibly be threatened with violence. Same with other religions. A lot of people are just trapped, or at the very least don't want to deal with the social consequences of choosing not to be involved in their parents' religion.
Yes the average Muslim could just quit islam if he wanted to, in fact many do. Only the most extreme countries still force there citizens to follow a certain path, the rest of us are free to an extent.
It doesn't matter the consequences people still choose to follow or not to follow. People get disowned by there family for plenty of reasons but they still chose do to what makes them happy.