Answer:
Step-by-step explanation:
Because society has to decide what should be taught. What exactly are you training someone to do? Are you asking them to be good with the mind or good with the hands? The curriculum that results will entirely different because of that emphasis. You can't do both. Neither will be adequately served.
And believe me that debate is not trivial. The province (Canada) that I live in just overturned a good program put forth by the previous government because they did not believe it was grounded in basic skills (reading writing and arithmetic). Our society is far too complex to limit learning to such fundamental skills (though they are very important).
Then there is the question of testing. How is evaluation performed? That definitely has become a social issue. How do we know that teachers are doing their job? Simple. We test the product (the students).
But the same thing that made the curriculum complex makes the testing complex. There are all kinds of issues involved in testing and most of them depend on the philosophy of the government paying for the education.
And those are only 2 issues. There are many more. Just ask a teacher.