I am a dyed-in-the-wool 1911 lover, but I also agree the Glock, and any of the the other 'plastic fantastic' guns could make more sense, if not from a reliability, then from a capacity standpoint, but when has .gov ever made sense?
You may laugh, but it all shakes out to two things when it comes to the .gov buying the 1911: the manual safety and hand fit.
For some reason, the military ordnance guys have seemed to always lean on guns with a manual safety...... and from my own witnessing at the range, the 1911 can fit hands that the Glock can't. I've seen folks who couldn't reach the trigger on a full-sized Glock be able to fire the 1911. Not all hands are the same.... I've seen kids with unusually long monkey-fingers and 300 lb guys with short sausage fingers...one does not set the example.