Earlier quoted context omitted.
The reason it can be done in China is because those shops illegally obtain the parts (whether counterfeit or stolen, since Apple won't intentionally sell them to anyone) and resources (schematics, software, etc) to be able to do so. This situation is both good and bad. Stolen parts are good, in the sense that this grey market at least allows consumers to repair devices cost-effectively. It's also bad, because besides…
It's a signal when humans will do something against the law - and generally it seems to be a fair response to excessive control or at minimum a counterweight to the actions of a selfish for-profit or industry. Piracy comes to mind as well: if content becomes too expensive, requiring monthly subscriptions to too many places or then unreasonable cost to buy a specific film or series - then more people will pirate, and…
For example, Prohibition, the war on drugs, gambling prohibitions, etc.