I've watched both Norm and David Marks turn bowls on TV. They both cut their bowl blanks the same way.
Why are the bowl blanks cut perpendicular to the rings of the tree? I would have thought that to do a bowl you would just cut the end off of a log and mount it on the lathe and go to work.
My uneducated guess is that it has to do with either strength or expansion/contraction. But, Really I have no idea.