I think this is not so much a "law" as a failure mode. It up to the programmers, objectives, time constraints and economic considerations whether a concerted effort is made to increase code quality or to go for the "quick fix" at the expense of long-term maintainability.
Anything that changes continually with a bias toward preserving existing structure ends up looking like biology in some way.
When people add to existing methods rather than creating new methods, or add to existing classes rather creating new classes we end up with that organic feel. Fruit starts green, grows ripe, and ends rotten.
The fact we need to face is that this is what people do naturally. It's not an accident. It's more like behavioral economic incentive.
