Actually the most significant reason to not cite Wikipedia is the churn -- citations are supposed to give readers enough information to actually find the specific information that is being cited, and that should be possible even decades after a paper is published. Citations to academic journals are generally preferred because journal articles can, in principle, always be found because of the archives maintained by university libraries. Citations to Wikipedia articles would need to include the specific revision being cited and there is no guarantee that any revision of any article on Wikipedia will actually be available 50 years from now.