On Mon, 22 Jun 2009 15:26:28 -0700 (PDT), "
wrote:

I want to
know for my own benefit, since I cannot find an explanation other than
"it just is". Just like lots of other things science hasn't explained
yet. Not "can't",..just "hasn't yet". And the invitation stands for
anyone.

Some things are just tradition and "just is". No need for an
"explanation".