Why is math education important in public schools?
The vast majority of students will not be mathematicians or accountants, and will not have any opportunity to reinforce the information they learn, and hence will forget it all by the time they are 20.
--OR--
Why is english education important in public schools?
The vast majority of students will not be writers, and will not have any opportunity to reinforce the information they learn, and hence will forget it all by the time they are 20.
--OR--
Why is history education important in public schools?
The vast majority of students will not be historians, and will not have any opportunity to reinforce the information they learn, and hence will forget it all by the time they are 20.
--OR--
Why is physical education important in public schools?
The vast majority of students will not be althletes, and will not have any opportunity to reinforce the information they learn, and hence will forget it all by the time they are 20.
You can apply this argument to pretty much every school subject - so your question is really "why do we send children to school"?