no setters for page elements?

I'm just wondering why the generated Java source for my HTML contains 
getters, but no setters for elements I've defined in a form.  For 
example, to set the value for the first name on my form I need to do:
form.getElementFirstName().setValue("Matt");

This is no big deal, but I'm just curious why there isn't a 
setElementFirstName(String s).  I'm sure there's a good reason.
  Thanks,
   -M@