Another (admittedly debatable) counterpoint:
Do it...but don't use the fancy, tricky to learn, time consuming spline based routing environment that Inventor and Solidworks provides. We're looking for fast, dirty, and easy here...if it works for wiring the real thing, it should work for CADding it, right?
Don't even try to be that realistic. Equation curves? Splines? 3D sketches? Too much time! Stick to basic sweeps off of 2d sketches, and even then, only straight lines and arcs. That'll cover most everything. Funky bit where this doesn't work too well, like a wire looping from a PDB port down to flat with the bellypan? Don't worry about it, it was small and probably insignificant. We're after the big things.
Still, it seems like a lot of time and effort. So find ways to make it easier. Lots of wires taking similar paths? Model them all together on a single sketch packed in tightly and systematically, or maybe just as a
single tube. Go out of your way to have as many wires in that path as you can, it'll save you that much more time, right? Spending lots of time finding models of all your connectors? Work to standardize, maybe even replacing bunches of little connectors with options that can be approximated as
one big block. Trouble squeezing wires through a small space? Make it bigger or adjust your routing, it was probably going to be tricky in real life anyways. Losing track of where wires are going to/from? CAD lets you colorize things with a click of a button, maybe develop some kind of labeling system based on that. Can't set up your work planes quite right to get a wire to run through space the way you want? Just build it along pre-existing structural members instead. Still running out of time? Just say that some wires go through a tube piece -- no one will ever know they aren't actually modeled, right?
What you're left with is an approximation, which may not resemble the way you currently wire at all. Extremely straight lines, with a lot of wires taking the same path. Very little floating in free space. Lots hidden by structural members. Multiple connectors replace with one...
...hey,
this is starting to sound pretty great, isn't it?
Of course, you've still got to follow through on the actual fabrication. But that can be a lot easier with a picture in front of you of how it's all supposed to go.
Being lazy about your real-life wiring leaves you with lousy wiring. Being lazy about your CAD wiring can accidentally give you great results in real life.
Of course, even this method is still near the bottom of the list of "productive ways to spend CAD time." This is only helpful if everything else is basically all set.