it seems Owen (SkiFreak) has skills which others may not imagine. A perfectionist. Meticulous. A jig for everything. Fine Engineering Tolerances. Pride. I know we are having an election in Aus but fortunately Owen isn't a candidate. I was going to say never makes a mistake but that would be one superlative too far.
For my part, if I can't find someone to perform a task to my expectations I look elsewhere or do it myself. Not sure where 1/64" came from as being acceptable, half a mm is a lot. I'm not a fitter, nor do I have Owen's skills, but I can file something flat and square to less than 1/1000". I was taught so I could appreciate the skills of those who followed a career making and maintaining things. Access to a reasonable workshop helps - my lathe is getting a bit tired.
The simple reason for tight engineering tolerances (as different perhaps to building tolerances) is it makes design easier, things fit without rework, build time is less (though Owen may disagree on time for a part at least final assembly is order of magnitude shorter), longer life, maintenance is easier and less time to repair.
The consumer world is very different to the heavy industries I worked in. Most of what we buy for our trucks is consumer grade, built to a price not a quality. With specs and quality that owe more to marketing than engineering.
I learned a new textonym a few days ago which seems relevant ............ ymmv ........... Owen's post wasn't a defence, it was simply a statement.
