What is the primary reason for the growth of the tertiary sector in an economy?

The primary reason for the growth of the tertiary sector in an economy is the increasing demand for services as people become wealthier and lifestyles change. As economies develop, more individuals have disposable income to spend on things like healthcare, education, entertainment, and travel. This shift happens because people often prioritize services that improve their quality of life over producing goods. For example, in a growing city, you might see more restaurants, gyms, and schools opening to cater to the needs of the population. Therefore, as societies evolve, the tertiary sector expands to meet these new demands.