Road Warrior,
I repeated a post that I had seen previously, and have no specific knowledge of the bicycle industry.
I do have over 20 years experience as a manufacturing engineer in metal cutting and forming. From the standpoint of just making a metal BB shell, a press fit shell has the potential to be significantly less expensive. Now, this is based on many assumptions, but if the opposing threads have to be in line in a tight enough tolerance to support separate bearing cups, you may be looking at single pointing threads. Everyone thinks you just slap a tap in a hole and get threads, and you do, but you do not control location of the pitch diameter.
Location never mattered with square taper bb's, because the bearings were located to the spindle in a stand alone assembly, and the shell alignment had no impact on the bearings, only on crank alignment to frame. With outboard bearings, the bearings are only as good as the PD alignment half to half.
Anyway, I'm not saying that it didn't bring weight reduction or other advantages. But to say it didn't have cost benefits to the manufacturer may not be honest either.