Why is a teenage pregnancy hard?

Because a teenager is not an adult. A teenager has not had the time, experience of life, or know how acquired to properly care for and raise a kid on her own. She is emotionally, physically, and mentally immature.

It is hard because it is not the way it should be. A kid should not have to raise another kid. The difference between a 16 year old and a 26 year old is ten years of growth, experience, and knowledge that make a huge difference.