Organisations design systems which mirror their own communication structure.
“Any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization’s communication structure” — Melvin E. Conway
The software interface structure of a system will reflect the social boundaries of the organisations that produced it, across which communication is more difficult. Small distributed teams more likely to produce more modular service architecture. Large colocated teams more likely to produce monolithic architecture.
So what? Communication paths and interaction between teams matter. Org structure matters. Conway’s law is more of a heuristic than a scientific principle, but it’s absolutely logical. Communication is the principle thing happening in organisations, and design will follow the path of least resistance.