🚀 go-pugleaf

I can give you one reason for not MIRVing without SALT 1,
it's dumb.  Sure it saves a few bucks being able to hit several
enemy targets with one launch vehicle, but the launch vehicle
has to be bigger to handle the extra warheads and the MIRVing
mechanism, and it's much more vulnerable to enemy sabotage or
enemy first-strike against it than a bunch of single-warhead
missiles would have been.  Stockman might suggest MIRV as a budget
cut, and a scientist or engineer might suggest it just because it can
be done and it's sort of technologically challenging and a neat hack,
but I doubt a military genius would like it unless forced upon us by 
the launch-vehicle limits imposed by SALT 1.
I'd be glad to hear rebuttal from somebody with lots of military know-how.