Ok, as a teacher, that's absolutely ridiculous. Students and parents would lynch me if I had that mentality, and rightly so. If a student turns in a great essay with minimal errors, they get a perfect score. Again, why have the number 10 if it's never used?
I know plenty of teachers who'd disagree with you. Then again, they use a grading system that's got a margin of uncertainty less than 10% (i.e. out of 20 or 100).
You certainly can't just assign the maximum mark to the best student in the class. That makes the grading system relative, which is a very bad idea.
Why is a grading curve bad?
Because sometimes the difference in grades is like 40% and 100%, and giving someone like a 25 point curve isn't fair to the person who worked/studied hard for the 100% grade.