What if i told you that the high school around the corner from my work has a 3d printing group that gets kids started on Google Sketchup and has them making their own 3d models within an hour? Sure Sketchup is much much simpler than Autocad or Solidworks, but the principles are the same and the techniques are additive; once the user knows the techniques, they can be transplanted from application to application, with the widely varied interfaces between different applications being the biggest hurdle. Some of these kids have produced functional multipart models in blender after as few as 10 hours of supervised play.
I agree that this is totally different from functional design, but engineering and 3d modelling are actually fundamentally different skills...
Also, blender (and 3dsmax, and maya and zbrush... but blender is free & open source) has supported native .stl export for a while now.