As a former installer I would ask " Why are car audio customers so cheap and stupid?"
I'll admit there are some bad shops but 90% of the janky work you see is "exactly what the customer wanted." And who am I not to take there money and do exactly as they request?
Customer: I want four, 6x9's in my dashboard.
Installer: Are you sure about that?
Customer: Yah, dat be ballin.
Installer: Umm, ok. But we'll need to do some fiberglassing and then wrap it vinyl so it looks right. (even though it will never "look right" or sound right) If you drop that off today I can have it done before we close tomorrow.
Customer: Tomorrow? I can't be waiting that long. I can drop it off on my lunch break and you can just cut some holes with that saw thing you got. Shouldn't take more than an hour, man. Dats how my boy did it in his ride.
Now, I can refuse this job and wonder how I'm going to pay the rent. Or can take the job, pay the rent, and pray to god another customer comes in with some common sense and some money so I can flex my skills and hopefully redeem myself. This is a business, not a charitable organization. Bills have to be paid, I have to eat, my family has to eat.
Being an installer is far, far, far away from being a glamorous job. If you think you'll only be working on show cars you're sadly mistaken. Just look on this board as an example. How many times have you seen someone post up pics of their home brew install and there is a 3 day old cheeseburger still on the floor board? And that's coming from someone who supposedly "cares" about his ride and is showing it off to the whole world on the web. You can only imagine what you'd see other cars.