I am a field Property damage adjustor for one of the larger companies. You, I promise, get what you pay for. Most of you that pay the cheap premiums have cheap insurance. Post above is correct on most of what he says, All companies tell you ahead of time if they pay for aftermarket stuff and how they justify it, just that most (all) of you have probably never read your policy. This is not very prevelent on Motorcyles as aftermarket parts are just not out there. Aftermarket stuff (car fenders, bumpers, radiators etc) are built based on demand, drive a Camry, almost everything is available a/m. Drive a current year or two old Impala and no one makes a/m yet, so you aren't exposed to it. Preferred shops are, regardless of what anyone says, to your advantage. Your insurance company, not just the repair shop, will warranty the repair if done at a approved shop. Why do you care if a discount is involved, you only pay your deductible anyway. No reputable shop/insurance company puts any parts on your car without discussing it with you first, you do realize you have to sign authorization to repair before shop starts, or you don't have to pay for repairs, this is when you discuss parts/repairs etc. You have the responsibility to OK everything. If they are going to use something you don't agree with, express yourself at this time, or look at it like your health insurance and pay the difference for what you do want.
Now the one thing that is very scary, to me, is the concerige service offered by a few companies, where they choose shop, you only drop off and pickup, This is for those people who want no say, responsibiltiy in the repair and those folks deserve what they get.