I have worked in many genres of technical art: automotive, medical, various science topics, how to build it yourself, and or how it works - type tech art - example solar energy solutions. I have also done basic manual type how to(s) for auto maintenance publications.
Above example are all from freelance jobs. The Fleet Crew mining truck (bottom) is the latest of the illustrations above. I was hired as a subcontractor for an agency to do a vector rendering (so it could be scaled as needed with no worries that come with raster art) of one of the modified Toyota trucks they use along with the equipment package pieces they put together for the vehicals. This piece is an example of mid range rendering. By that I mean adding gradients to shape the object to give some dimensionalty to it. Full blown slick rendering can be seen in my general portfolio "SAMPLER PAGE: Vehicles - Auto Art"
The racing seat with harness is from a direct hire job (no agency middle man). The company was Fox Pro Racing. I did two illustrations - the one above and another with a different style seat. It is a very typical type of line art tech illustration.
The side view of the head with head gear was part of a series of views showing how the gear was to be applied to a patient.I did that one several years back and can't remember the company offhand - will have to dig that out of archives when I get the chance. You can see some of the other views in the general portfolio "SAMPLER PAGE: Technical Illustration"
The final piece was for a small company the made bait tanks.This was also done many years ago, and I will have to see if I can dig up their name. Part of the design of the bait tank included an apparatus that created an artificial current for the bait fish to swin against.

Some commercial work / projects / clients I have used my tech art skills for directly, or as a sub contractor for an agency:
Fleet Crew (tech art shown above)
Fox Pro racing gear (tech art shown above)
Other work as noted up above has been in science and medical genres. In these instances I have done illustration work for Doctors who authored books, dentists and dental products, research scientists, and companies (one offhand - Stem Tech). When I get a chance I will add an indepth page for this segment of tech art.

So... Technical art... why? It is an area I slipped into. I say slipped into because part of me liked engineering and another part was all artist. So technical art sort of bridges these two seeming desparate endeavors. Probably for the same reason - web / basic web coding stuff was easy to slide into for a while as well. The old stereo type of creative not being technical and vice versa does'nt seem to apply - and I am not sure if that notion was ever valid. Were I the type to quote / name drop - I would post a quote from futurist Jacques Fresco on the bs of the word creative.