Bmblbzzz wrote:@Cugel: Testing the fixers -- good idea but does assume some knowledge on your part. Which brings us back to my point that people do use machines they don't fully understand, because otherwise our lives would be restricted. Numerous examples from the inessential through the useful to those we really depend on. I'd suggest the ways of "testing the fixers" most people use are recommendation from friends and relatives, and judging by results -- how does the thing work when the fixer has finished? Find someone who's good based on these criteria and stick with them.
Four basic categories of reason for not fixing an item yourself: physical ability, mental complexity, circumstances (time/space/tools), lack of interest. Perhaps the last is less "acceptable" but then a lot of machines are not intrinsically interesting - we're not all engineers!
To make this at least tangentially relevant to disc brakes: I have them on one bike and I change the pads, adjust the pistons, etc, myself. These are cable discs - in the past I've bled hydraulic brakes on motorbikes and it's a pain, (fifth reason for getting others to fix things; to avoid nasty substances!), which would disincline me to use hydraulics, but if I had them... well, I'd have to see. Meanwhile, my friend N has a disc-braked recumbent trike with electric assist. She needs the electric assist due to mobility problems, and the weight of the battery (and it being an inherently heavy recumbent trike) probably make disc brakes a good idea - anyway, that's what it comes with (can't remember off hand if they're cable or hydraulic). Those same mobility problems (or rather, other associated disabilities) mean she physically can't fix the thing herself - she doesn't have the manual dexterity.
You're right to note that all of us (including me) have become reliant on technologies we don't understand well enough to be able to fix ourselves. A modern car is one example and an electronic camera is another. Although I was once the car maintainer (from oil change to crankshaft renewal) this seems impossible with a modern car for we ordinary folk. Several electronic gubbins are black-box and inherently unfixable anyway, even by an expert.
One response is to do without these items. I would like to do without a car and perhaps will do before much longer. Already I go days and days without driving it. I would be reluctant to give up a digital camera, though, even if photos are not essential to life. On the other hand, I've never had a mobile phone or several of the many bike gizmos and never will have.
The other response, as you mention, is to evolve better tests for discovering and testing competence in expert maintainer-fixers of things we may want to use but can't fix ourselves. The basic mechanism is "reputation" but this is very hard to discover. Every good and service seems, these days, wrapped in layers & layers of hyperbolic advert lies and pseudo reviews). The only way to test a fixer is to use one and observe the result - which, if no good, has still cost you a wodge.
However, I use the reverse reputation test: one convincing and evidenced bad review means the good or service is crossed off my list of potential providers. It might mean I miss a good one but if it means I avoid ten potential bad ones ......
If there are 99 good reviews and only 1 bad one, I employ the law of probability and don't cross off the potential supplier. But even that's a gamble. More and more I go for the "I don't really need or even want one" solution. Also, I learn new skills, such as how to bleed hydraulic disk brakes properly. Some things do remain self-maintainable. Why remain incompetent at doing it yourself? That would be like getting someone else to watch a play for you then give you a summary. Or like having a servant to dress you, cook your dinner and weed the garden. Personally I have always abhorred the aristocratic mode of life.