> Also, most Catholics are born in catholic families so it's not like they chose catholicism over something else.

I do not know whether that is true any more, at least in all countries. At one Catholic parish I knew in Britain about half the congregation were adult converts.

Then there are a lot of people who leave and return. I might count as that - Catholic family, was agnostic (and married in registry office, which turned out to be useful), and now am definitely a Christian but feel denomination does not matter and do not really accept much of the Catholic theology (and some of its practical consequences, such as no women priests really bother me). OTOH I have not, and would not, formally leave the church either.