Get self-satisfaction: Educating others can make people feel very full and proud, because they may help others solve problems, acquire new knowledge and skills, or see their students or colleagues make progress in their careers and lives.
Achieve personal goals: Some people may engage in education because they think it is a way for them to achieve their professional and personal goals, or their sense of social responsibility and mission urges them to help others get better education and development opportunities.
In a word, I like to educate people for different reasons, but all of them can make people feel satisfied and meaningful.