Collapsing vertical margin through parent. why?

I was wondering if there is any reason that the vertical margins of a
block level element should collapse through the content block of its
parent. 
I have yet to find a reason for such a behavior and i think that making
the parent accomodate the margin instead of absorbing it would make a
lot more sense. 
While i can stop the behavior by adding either padding or a border to
the parent his forces me add extra properties to achieve functionality
that should be able to be obtained by default. It also makes my CSS file
ratehr unreadable. I have an example of my dilemma at:
http://www.insitesinc.com/problem.html

Thanks for any help or explanation.

-Michael Favia