We count many things and phenomena. Counting is just a form of measuring.
We measure to understand how objects, systems, societies or organisms work.
We measure how fast a car can go and how much fuel it uses. Some people base their decision about the car to buy on how many miles per gallon the car can do. 
We measure the health of human populations by counting cases of diabetes, cancer or coronavirus in a given population.

The same happens with the health of animal populations, such as bees in beehives. Various types of measuring can provide valuable information about how a population of a beehive changes, and scientific research does exactly that. 

Typically, in beehives of the Northern Hemisphere, the population of adult worker bees decreases in January and February, reaching the seasonal low sometime in February/March when the count drops to about 20,000 individuals. As the day length and pollen availability increase, between April and June, the birth rate starts exceeding the death rate and the colony population rapidly grows. Sometime in June, the average beehive’s population peaks at about 60,000 individuals. Weaker colonies either have a lower peak population or reach their largest size later in the season.

Source:
The Mid-Atlantic Apiculture Research & Extension Consortium, Basic Bee Biology for Beekeepers; Fact Sheet,MAAREC Publication 1.4 March 2004.

https://canr.udel.edu/maarec/

We know how the number of bees in a healthy colony fluctuates over time, according to the seasons. 

A healthy colony grows, collects pollen and produces honey.
Counting bees, day after day, during the whole season will deliver a similar graph for a healthy population. 
The graph above is a good illustration of this process. 

A significant divergence from the “normal graph” showing fluctuation of the number of bees in a colony indicates a problem in the health status of the colony and should prompt the beekeeper to inspect beehives in question.

Let’s go back to counting. But this time, let’s count money. 

Bees and beehives provide valuable goods and services, and thus cost money and bring financial benefits to their owner. 
With this in mind, let’s consider a case of a migratory beekeeper with a pollination contract.
Counting bees in every beehive at the pollination location will inform the beekeeper about the health of the bee stock at hand. 
If the numbers decline during the pollination contract, the beekeeper can make an informed decision about the cost vs benefits of the contract, (and place a legal clause in the contract reflecting potential losses in the used bee stock).

A similar logic can be applied to a bee farmer with apiaries in multiple locations.

Counting individuals within colonies provides a quick insight into the health of the worker bees. If the farmer can easily see how many bees are in their colonies, any difference between the “normal graph” (as shown above) and the actual population count, will enable him/her to prioritize inspections and save money and time on unnecessary trips.

Somehow, I have managed to move from bee counting to bean counting.

Bee counting is another tool in the beekeeper’s bag of knowledge.
It will help to verify efficacy of modern and traditional treatment methods. Test the “medicine” and back the experiment with data.
Simply make notes about type, amount and concentration of the treatment, sit back and watch the numbers change.
And make informed decisions regarding this particular treatment in the future.