You have a package delivery business. The business is stable and optimized, serving all houses in your city. Each courier has a route planned out that they follow each day. They take 8 hours to complete the route and deliver to each house along the way.

Now, cars come along. With the new efficiencies, you find that now a courier takes only 6 hours to do their route. The number of buildings in the city has not increased, there's a cap to how much service you need to provide after which there's no longer any additional benefits. So, do you cut everyone's work day to 6 hours, or do you fire 25% of all couriers and re-route the rest so they now do 8 hour days on longer routes using cars?

Your solution assumes that the extra workforce immediately translates into free growth, but the growth of many businesses is constrained by outside factors. Here it would be the population of your served area.