[CQ-Contest] Why the 10 min rule anyway?

[KI9A at aol.com]

Excuse my ignorance, and, not condoning the recent DQ's.  
 
But, what is the idea behind the 10 min rule for M/S, anyway?  It's  still 
a single transmitter, just multiple operators.  What makes this any  
different than a S/O making band changes?
 
Just wondering.  Seems to me like a really silly rule...that's why I  need 
a decent explanation of why.
 
73- Chuck KI9A
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