Your first paragraph defines what I saw in Germany. With a certificate with many stamps on it saying you were qualified to do something, the average German defaulted to "knowing" they couldn't if they did no have that particular cert.
The second one has still never worked out for me. I am a less extreme example of what you described...I make about twice as much as I would spend for mundane repairs to home or car. I use quick oil change places for my truck and DD. I do not mount my own tires.
That said, I have never found a "savings" from having a professions do even a moderately big job around the house outside of having a roof done or a furnace installed. The reason is their unreliability and inability to finish on time and clean up after themselves means I spend more of my valuable time waiting on them. I went through this recently (twice) when helping others' prep their houses for sale...trim guy took 4 days longer than planned so paint guy could not get in on time so he pushed out a couple of weeks to go to other jobs and electrical guy no-showed twice when I took time off work to meet him and let him in the house (In the end, I just did that work), etc, etc.
When I redid my kitchen, I had it gutted, drywall hung and ready for mud and tape. Since I was on a really tight schedule, I hired a company with very good references to get it to primer. They said 3 days so I offered a 10% bonus to be done on time and added that to their standard contract. They finished the morning of day 5 so I had to pull and all-nighter to finish flooring. They also used no system (zip walls) to reduce the amount of drywall dust getting in the rest of the house and did not use the primer spelled out in the contract so I still had to re-prime the one original wall.
The last contractor I hired was a hardwood floor guy. I made it clear that the ONLY window to do the work was 5 days while I was gone to the track and the dogs were at the boarders. I moved all the furniture out of the rooms before I left and re-iterated to him that this was non-negotiable (boarding all my dogs is about $100/day). I returned home to find he had not yet started. I changed the locks, used his machines to do the work myself (the sanding and screening after stain). I called him after and told him the machines would be in my driveway at 6 am the next day so he probably ought to show up to get them...that he showed up for. This one cost me $580 in boarding fees, a twelve hour night getting to second coat of stain, three hours a night for three nights getting the poly (screen, vacuum, wipe down with alcohol, apply) down and $40 a day for buffer to screen between coats. It was a $1500 bid on the job.