Because Maintenance has the same cancer that plagues the rest of the USAF. Good people care about the mission and want to turn a jet for a mission. And there's other, more senior people, who only care about offduty education, volunteer opportunities, and face time (sts) with senior leaders to get that next assignment, job, or strat.
After being in a AETC assignment, with contract maintenance, I'm very skeptical about the quality, compentency, and honesty of an AD maintainer wearing less than five stripes. Sometimes it feels like my crew is buying a used car when reviewing the forms of some jets and asking about certain write ups.