Well, it's not done everywhere. There are countries that my friends did tell me about that values their teachers even more than doctors and pay them higher. So I guess, it's just in some countries that doesn't recognize their importance and the impact they create in the society.That is actually the truth,teachers are the most under valued proffession,and i don't really know the reason behind that,they are suppose to be taken care of being that the foundation of the future leaders are being groomed by them.
Even though they are underpaid, they still sometimes pay them the little they earn as salary very late.