On my machine, and I suspect many others, the motor cables aren't nearly long enough anyway, so need extending. This being the case, my motor cables (i.e. the ones actually coming out of the motor itself) terminate in a little plastic junction box somewhere near the motor and therefore quite a long way from the "sensitive" cables (step/dir, etc) which are retained within the screened control box and use differential signalling anyway. Junction box to control box is via screened CY cable. My guess is that the combination of screening and, effectively, differential motor connection work to significantly reduce emitted interference. The long "signal" wires on my machine (limit switches and e-stops) use 24V for better noise rejection. The drivers also stay away from vibration and dust in the control box with a light waft of air from a couple of low-power fans to keep them cool.

However, as Doddy says, engineering is all about compromise and there is a whole bunch of trade-offs to take into account. I went for the easy and most common configuration but that's not to say that in other cases, a different solution might not be better.