Why do we Teach?

I think that we teach, first of all because there is a need for it, but also because someone somewhere made an impact on us and started us down that path towards becoming a teacher. Teaching is something that has to be felt from the heart, and it is something that one feels called to do, compelled to do. So, simply we teach because we have to - in a good way.
Student work sounds like mindless activities that are given to students - like busy work, but it is also all the assignments and, well, work that students do throughout their school year/career. Student learning, however, is different from work. Learning is what the student actually takes away from the classroom with them to apply elsewhere in their lives or later on in school. As teachers we should strive to make the work facilitate the learning - the two should go hand in hand. The work should be meaningful, so that the students actively learn form it and take something away from it. The work should not be the typical memorize and forget stuff that we are all familiar with.
I think that the above is what also makes a good teacher, along with other things, of course. Being able to relate to students is also important. A teacher should also push the students, not just kind of go with the flow. In my experience teacher's who just go with it and want to be your friend not your teacher do not make good teachers, they make the kind of teachers who frustrate you and give you a bad learning experience.