It's ignorance on both sides as others have said. It took me a good 8 years as a maintainer to find out why crews would hop out of perfectly working airplanes and kick someone else out of theirs. There are a bunch of other things that routinely piss maintenance dudes off but when you look into it or someone takes 5 seconds to explain it, it makes perfect sense. I remember seeing an E model squadron scheduling board for the first time and about shitting my pants. Its a simple fix but it will never happen.