As someone that also 3d prints screws, I can share my reasoning.
I am a westerner living in a non-western country. Communication with local people can sometimes be difficult, especially on the acquisition of technical components, including with screws. Often I need a specific kind of screw for a specific task, and often the screw does not need to be particularly strong. I would rather communicate exact specifications to a computer and get exact results than be at the mercy of polite miscommunication, and have to adapt all my printing to what is available locally.
I would also rather keep production as local as possible instead of outsourcing it to people I don’t know, or having it flown overseas.
In general, if I can 3d print something I need, I will. Having a database of parts, components, and tools is very helpful, even if it takes less time to just order it. There is a reproducibility, security, and satisfaction to doing it all yourself.
As an aside, I have learned something. 3d printing has enabled me to live better than I did before leaving the western world, because I can make things now I never dreamed of before. This makes me realize that we can distribute and localize significantly more production than previously possible.
I now believe every household should have a 3d printer and a laser cutter for this reason, and houses should be built with techniques and components that utilize both automatically as largely as possible. By democratizing production, power becomes much more distributed and equitable, without any claw backs of the old mechanisms of doing things.
This also allows easy repairs or expansion of a house. Something breaks? Print or cut the part and replace it from a library of parts. Everyone can understand raw materials no matter where you go, so the standard of living becomes planetary.
That is a part of the real change.
Aren’t eggs produced at industrial scales from chickens, who super-abundantly exist?
How is that working out?
In no universe does the economics of a $1 egg make sense, yet here certain countries are. Did you know you can have chickens in your backyard, and they’ll turn bugs and cheap feed into eggs?
The less you can offload production to central untrusted parties, the better. When you manufacture something yourself, you get to know all the properties instead of trusting that some people elsewhere (whose primary motivation is money) still considered your interests by making a quality product.
So when you say “we,” what does “we” mean exactly? It is rhetorical.
Additionally, you get consistent reproducibility without reliance on large scale logistical networks. There are many other reasons I can think of off the top of my head beyond this.
If we lived in a more cooperative world, with ironclad democratically owned logistics networks and manufacturing, centralized manufacturing would make sense in the way you say. But the reality is, we do not live in that world, and more and more, we are all increasingly feeling what that means.