Why did 19th century imperialism rely on local elites to rule local area?

The local elites controlled the areas through their vast wealth that was accumulated through trading and exploiting the colonies. The governments relied on them because they were useful and would not bother the government as long as they were free to do their business. The government would let them build wealth and trade with the origin country, while the elites would just earn even more and sometimes even get royalty titles.