In the scheme of things, bikes are NOT that complicated and no specialist knowledge is required to work on them. Any competent home DIY'er or DIY car owner could easily master anything required to be a bike mechanic. It does require some skill, but let's not try and make out it's rocket science to fix bikes, because it isn't.
Well, all is relative, what's easy for you might be complicate for me and vice versa.
I started riding regularly at 48, nobody had bikes in my family as a kid so no chance to pick stuff up. Of course, I did not have a bike either.
Fast forward to when I decided to find an easier way to work than the 2 buses each way required (I don't drive) I soon realized that I needed the bike to be reliable.
I made it my business to know how it works, and learned the basic maintenance.
Some stuff though I simply don't have the time to do, I work long shifts, have a garden, other commitments, if it's a nice day and I'm off I'd rather ride than fix something that would take me all day while the LBS does it in 5 min.
Other stuff, like stuck freewheels, take half a day because I'm not strong enough - again, the LBS does it in 5 min.
Then if you buy the parts on line, wait until they come, maybe my shifts don't sync with the delivery, wait some more, maybe I bought the wrong part ...
At one point I ended up with 6 bikes in various state of disrepair because I had no time to learn how to proceed, never mind actually fix them!
Then again, I might not be able to bleed brakes, but I can program an industrial espresso machine, I can speak 4 languages and I can ride 4 miles with a split seat post