Apple is notoriously draconian about ensuring that 3rd parties are blocked from accessing schematics and repair manuals. I'm talking, they threaten lawsuits to anyone publishing schematics, and there is no legal way to obtain those schematics unless you're an Apple authorized repairer - in which case you'll never need them because your job is just to replace entire logic boards after minimal diagnostics. This creates enormous waste and costs a lot more than an actual repair would. In some cases they don't even do that and just tell the user tough shit, get a new device.
Clearly you have not been to Asia. Plenty of 3rd party iPhone repair shops. Very easy to get batteries and cracked screens replaced.
I think people have been successfully conditioned to view phones as disposable/replaceable. It would take an almost Sisyphean marketing and conditioning effort to change that thinking.
I'm not sure it's possible. But, hey, I suppose Apple's free to try. No harm there I suppose.
Outside many European Apple stores they even often pay someone to stand and hold a sign advertising cheaper iPhone repairs available around the corner etc.
Anecdotally, a large number of my friends and family have all used these, usually for cracked screens or batteries, and often in preference to an Apple store on the (sometimes incorrect) assumption it will be cheaper than “taking it to Apple” to get fixed.
The reason they're everwhere is that people do take their phones in for repair. Mostly battery replacement and cracked screens. The town I live in manages to support three repair shops that I know of.