That is OK until you come to retrofitting something like an older Linde where the gantry weighs upward >300lb with 4 oxy/gas torches and maybe a plasma torch added.
With AC/BLDC servo's having a constant torque up to their rated rpm of 6000~10,000 rpm, high reduction allows the economic sizing of servo's on something like this, especially if you want 1000 IPM rapids .
I have found there is no hard and fast rule.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.