Having used some of the earliest 3D CAD programs when they were in their infancy, and still knowing how to use the newest versions of AutoCAD, I draw it by hand. If you know what you're doing from a drafting/technical drawing perspective, you can get a usable, dimensioned drawing in just a few minutes. Much easier to make changes and last I checked none of those programs do cutsheets so you still end up hand jamming it. If I was in the business of designing boxes and was going to be using production equipment to make multiple copies of each one, I might go to the trouble of making a CAD drawing. Even machinists with access to CAD-CAM and CNC don't bother building the computer model for a one-off unless it is a prototype for future production or super complex, they just make it manually.
Sketchup is a total waste unless you just are unable to picture something in your head. If that's the case you probably shouldn't be designing anything. As far as showing off your design, build the box. Take pictures.
And your *** analogy sucks. *** is better with a partner. Your box design isn't better because you wasted the time to draw it in a 3D sketch program.