And yet Office still boots twice as fast as OpenOffice on a typical computer, IIS and MS SQL are completely neck-and-neck with their competitors, and Outlook completely trounces its closest competitor, performance-wise.
I mean, I completely understand what you're saying: having multiple copies of the same function/code block in memory is inefficient. But in practice, it doesn't seem to be hurting them anyway.
Man is the best computer we can put aboard a spacecraft ... and the only one that can be mass produced with unskilled labor. -- Wernher von Braun