Idk about your premise. Kids don't really spend most of their time in the first 25 years preparing for a career.

School is a lot of wasting time for waiting for kids to grow up. You can tell this is true because how some kids can catch up the learnings of a year over the summer if they were missing due to illness or student exchange or vacation etc.

Kids also spend a lot of time playing, watching tv, doing sports, learning instruments. My school education was also a lot of useless arts and culture and theatre and learning useless stuff by hearth. You could say that's part of preparing for the softskills part of a career - but at least you have to admit it's debatable here.