In a addition to that, even accommodating a BDC isn't as simple as just zeroing at 50 because the manual said to. As you said, 50/200 almost never works out and chances are you aren't shooting the exact bullet at the exact speed in the same environmentals that the reticle designer input into his program when he spaced his stadia hashes.
I'm a big BDC fan for what I use 5.56 guns for and to get the BDC's to line up out to at least 600 yards (about as far as I find them trustworthy and as far as I need a 5.56 gun to work) I have guns zeroed at all different distances. Note also that most BDC's are designed around 55-62gr bullets going pretty quick. The 69-77gr stuff that most of us are sending out yonder start out with a velocity disadvantage that is eventually cancelled out by the BC advantage. So again, the manual specified 50/200 never works out. I've got BDC equipped guns zeroed from 170-190 and 210-230 yards depending on velocity to get the BDC lined up perfectly, but not a one of them at exactly 200.
But now that I wrote all that out, my more precision oriented guns with mil reticles are all zeroed at 100 for simplicities sake, which is probably more what the OP was asking about.