Instantiating ActionForm to pre-populate

I was searching around and found a very long thread in the struts-dev mailing list (of which I am not a member) about how to instantiate both ActionForm and DynaActionForm objects in order to pre-populate a form (see below for a snippet of that thread). My questions is, why go to all the

RE: Instantiating ActionForm to pre-populate

Charlie wrote: My questions is, why go to all the trouble of instantiating the form yourself in your Action, when the ActionServlet will do this for you if you specify the form-bean name in the struts-config.xml mapping for that Action I think a major reason that people are under this