Can you please explain why cirrhosis is not considered a disease found in young people?

It could be: It depends on what you consider young. The reason cirrhosis is considered a disease of mid to older age people, is because it goes unrecognized for years. It can be present in your 20's, although much more infrequently. Cirrhosis = scars in the liver and that takes time, occurs because of chronic inflammation (from viral hepatitis, alcohol, metabolic, fatty liver, etc.) if concerned, see a doctor.