Tangible items help inspire. The kinds of eclectic things inhabiting my desk right now. A hermetically sealed
6.3V 400Hz filament transformer. A 400 Hz synchro. An ohmite ceramic rheostat. A handful of proto boards. An AFL27005S thick film hybrid DC/DC converter (Lambda Adv Analog now IR). A plasma ball. A disassembled GPS navigator awaiting a fix. A couple of stud mount diodes (400V, 250A). Plastic box with miscellaneous resistors and capacitors. Some ferrite cores of various sizes and materials. A couple reels of SM caps. A 150 amp current shunt. A Red Lion Controls counter.
And that's just what I can see. :-)
I think a lot of it has to do with filing systems and accessibility. A big flat space where nothing is more than a layer deep is a pretty time efficient filing method. However, it's not very space efficient; hence the messy desk.
I'm guessing the desk will take a two week path from clean to messy, with the time increasing or decreasing based on the number and size of tools and parts needed during that time period.
Keeping a clean desk just to have a clean desk is a non-value-add activity, (IMHO).
However, if a desk gets messy enough to inhibit design or other activities then the desk/work area should be cleaned up...
I once had a sign above my desk; "A clean desk is a sign of a misguided career."
Any time I have tried to keep a clean desk I can't find anything. Let it me and I know where to find things. Basically I work best with an archeological filing system - the further back when I last worked on it the deeper in the pile it is. I do keep a "common work" area free and always available though.
Years ago, while an engineer at IBM I got in some trouble after posting the sign "A Clean Lab is an UNUSED Lab" during a forced lab cleanup for a management walk through. I was upset because I had to disassemble a working test system, and then had to rebuild it from scratch, starting a few minutes after the walk through!
I worked for a company in the 90s that adopted some silly management concept of changing things just for the sake of change because "it would increase productivity". Everybody's office got relocated except mine. I found out years later that a director had said that they would have moved my office also but it would have shut the company down for 6 months. Now that is messiness of legendary proportions.
I had an archeological filing system with a slope towards the front of my tables. When stuff started falling off the front of the table I would SELF-IMPOSE a cleanup of sorts.
There was a time (before e-mail) when my in-tray would become so overloaded, that I would take a large envelope - stuff it - and mail it to myself (through internal mail)... It would usually take 2 days to return to me, giving me time to sort out the remainder of the contents in my tray...