Answer:
Quechua is still present in modern-day South America because a large percentage of the populations of Bolivia, Peru and Ecuador (the current countries where the Incas lived) have Native American ancestry and, therefore, continue to keep their culture alive, including language.
Quechua is a language spoken by about 10 million people in the Andes Mountains of South America. It was the official language of the Inca Empire, and it is one of the official languages in Peru, Bolivia, and is also official in some parts of Ecuador.