alt Hacker NewsLibraries do a LOT more than that. Abstractions also make LLMs more efficient, and lets some problems be handed off to much cheaper algorithms. They also mean that the way data is handled can be standardized which means you don't have to design an entire protocol from scratch every time you want to send data somewhere.
Every advantage libraries have given us still exists in the world of AI.
The efficiency argument I accept, it's surely one main driver why systems tend to form and centralize and one important factor in the balance. Still, one can observe the weird things humans and AIs do when trying to dance around the gaps in leaky abstractions. So there's a tradeoff between (the effort spent on) that, and dropping the abstraction completely, as soon as the abstraction stops being a necessary constraint (due to the limited capacity of a human brain).