Why do all artificial satellites of the Earth, except for stationary ones, have elliptical orbits, and not circular?

They prefer to launch a satellite at a slightly higher speed than a circular one, since its lifetime is noticeably longer than a satellite launched at a circular speed.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.