It's actually the opposite - even a mundane part like the lug bolt you describe will go through several hardening processes, and post-processing for corrosion resistance. If not, you're asking for a huge failure on a critical part. This is an easy example - it's amazing the diversity in processes and materials needed to manufacture products from base materials.
Even in a ballpoint pen, there a good 5-10 dies needed to make the body and cartridge holder, pretty exotic processes to make the tip, a non-trivial pad-printing for color, and many other post-processing needs. Yes, we could reengineer products to not need this, but you're going to see increased costs and decreased performance - I.e. No one will buy it...
I don't think the screw that held my lawnmower wheel on went through several hardening processes. It might have been heat-treated to strengthen it, but I think typically you don't harden machine screws. Corrosion resistance, sure, it might have been galvanized or something. (But I doubt it.) The lawnmower wheel falling off as I pushed the mower did not constitute a "huge failure."
I think I adequately addressed the "increased costs and decreased performance, so no one will buy it" objection in my original comment. :)
"It's actually the opposite - even a mundane part like the lug bolt you describe will go through several hardening processes, and post-processing for corrosion resistance. If not, you're asking for a huge failure on a critical part."
That's at least party due to the different design requirements and constraints that mass-produced for-profit engineers work under. That lawnmower wheel screw was specified not purely on the engineering requirements to "hold the wheel on", but on various other important-to-the-company-designing-them-for-sale requirements, probably including things like: use the cheapest fastener that we already keep in stock that'll do the job, use a fastener that will reliably last the length of the warranty period at the lowest cost, use a fastener that's compatible with out existing automated manufacturing tools. On top of that there will have been other decisions already made like "use an existing wheel assembly" and "ensure the mowers packaged size and weight fit in with existing supply chain logistics".
Once designers are freed from existing manufacturing industry constraints, I like to hope that one day we'll download a push-mower design from somewhere like Google Sketchup, where the designers were perfectly happy to "over engineer" critical components and where the design requirements might include ideas like "should last long enough to pass on to your grandchildren", and "will still be able to be repaired at the side of the road with a flatblade screwdriver and a rock".
If you're arguing against standardization in parts - that's an uphill battle - sure once we have replicators it doesn't matter, but that's futurism.
I'm actively fighting for open source hardware and standards, but a big part of this is finding off the shelf components - look at Http://octopart.com for a good example of what this looks like.
"If you're arguing against standardization in parts"
Oh, very much not.
I'm more commenting on unnecessary overspecialisation instead.
Unnecessary for non-commercial applications anyway - I understand why Apple chooses to put difficult-to-use fasteners in their products, if for no other reason than to minimise fraudulent warrant claims, but there's a whole different set of motivations if designers are going to use the equivalent of "open source" for digitally reproducible home-fab ready "object" files.
Even in a ballpoint pen, there a good 5-10 dies needed to make the body and cartridge holder, pretty exotic processes to make the tip, a non-trivial pad-printing for color, and many other post-processing needs. Yes, we could reengineer products to not need this, but you're going to see increased costs and decreased performance - I.e. No one will buy it...