Why? For the same reason you can not
jump over rocks. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
The beginning of the
RPG World comic. <img src="/ubbthreads/images/graemlins/cool.gif" alt="" /> <img src="/ubbthreads/images/graemlins/up.gif" alt="" />
