While it has become accepted that tooling was designed for certain applications, a high speed drill doesn't face mill very good. The spindle that drives the tool is also designed for different applications.
Some try to design a spindle that meets every need, the torque required to push a large diameter cutter thru exotic alloys typically doesn't have the required speed needed to drill small holes. What if the holes are angled? What if you need more reach? What if you need to contour a surface?
Correa designed and built "automatic head changers" which allows you the flexibility to chose a proper way to machine on large parts. Why move a large part from a "roughing machine" to a "finishing machine"?