Why are there still human teachers? 
bofh: I'm sorry about all of you, guys who think this is a stupid question. You are all romantic people, saying there exist good teachers, and teacher is a friend of a student and blahblahblah. But the reality is - most of the teachers are BAD. I know much more examples of bad teachers, who even demotivate students, instead of inspiring and teaching them. And it is better to use a program, made by a good teacher, than to be taught by a bad teacher in person. 
And that is what the good teachers should concentrate upon, writing good pedagogical strategies for a teaching computer program. And don't be so ignorant - think about Chinese - they would need hundred millions of good teachers, which is not possible to have. And believe me, I had good teachers and I know what it means. I learned math, which is the most complicated thing to learn, and I still believe math teaching can be automatized to a big percent, without all these sentimental tears of joy about how good the human teachers are. Don't be so narrow-minded. In the future, there will be robots.