That's wrong on two counts. First of all, as someone who did convert, I not only didn't forget the traditions and cultures, but I teach my kids about them. I'm teaching my children ancient Greek in part so that they can read the New Testament in the manner that my grandmother did. They will probably know more about Christianity than many Christians before I'm done. Moreover, unlike Christians, I'd like them to know all about the various church councils that settled on the concept of the Trinity and how the power structure of the Christian church was born. Secondly, if the kind of websites you love so much are any indicator, Christian converts from Islam not only abandon the traditions and cultures, they go on world lecture tours to rail about them.