Isn't this true for high schoolers as well?
Young people who graduate from college early may not go on to make their major their life's work. If they don't, they still have a college level education in that field, and that will become part of the general education that will greatly enrich their life.
My youngest is considering becoming a physician's assistant or a nurse. She earned a B.S. in mathematics at 18. To earn that B.S. degree she needed to take all the general college courses, biology, chemistry, and physics. I consider that a very well rounded liberal education. She is well prepared educationally for whatever she chooses to do in life.
A well rounded education still serves you throughout your career. Sometimes it becomes a safety net when your desired trajectory doesn't pan out.