Certain teachers are easier, others harder. That's the way it has always been. Some movement has been made to try and bridge the gap in grading practices by creating standards. Others, like the Minnesota Profile of Learning, are an attempt to create truly challenging tasks that we can all agree on the level of achievement. Only time will tell if it will yield the desired fruit.
Grades are necessary.
I used to think that because they are essentially meaningless, they have no power. I was incorrect. Grades have great power to motivate, reward, demotivate and destroy. The overly simplistic answer is that good grades motivate and reward, bad grades do the opposite. Sometimes, I find the low grade is more motivating to a large portion of my students.