Why do professors scale marks and raise the marks of students that don't deserve it?

<p>In one of my high classes, a teacher would consistently have (out of a 22 person class) ~16 D/Fs, 4 Cs, and 2 Bs on tests. The material wasn’t hard; she just couldn’t write a test everyone without making it confusing. She wouldn’t curve; most people failed. Great class to take senior year, huh?</p>