[They start with the example of English words]
The second example Zipf showed in his book was the population of cities (or population of communities). The population of the city as plotted as a function of the rank (the most popular city is ranked number one, etc) is a power-law function with exponent close to 1.
The income or revenue of a company as a function of the rank is also an example of the Zipf's law (also in Zipf's book). This should also be called the Pareto's law because Pareto observed this at the end of the last century.
Neither city populations nor company revenues are designed. Zipf's Law describes an interesting deep pattern, probably having something to do with chaos (I don't know), but it's just not evidence of design. (Who decreed that English words would be used by people in a Zipf's Law distribution? Is there someone at the Census Bureau who keeps track of the distribution of city populations & forces people to move out of cities that fall out of the distribution?)
They are a consequence of design.