Conway's Law

Although sometimes construed as humorous, Conway’s law was intended as a valid sociological observation. It is based on the reasoning that in order for two separate software modules to interface correctly, the designers and implementers of each module must communicate with each other. Therefore, the interface structure of a software system will reflect the social structure of the organization(s) that produced it.
— via Wikipedia

Never thought about it this way, but it does make sense to me based on experience.