Insurance Companies have Direct Repair Programs in place with body shops. The Insurance Companies send their customers to these shops, and in exhange the shops may cut corners to save the Insurance Company money. The shops enlisted in these programs are commonly referred to as "preferred", "recommended", "network", or "selective" shops of the insurance company. The Insurance Companies have guidelines and regulations in place for body shops who are on their "list", and may force the shops to do things that they would not otherwise do.
Direct Repair Programs that insurance companies have in place with "preferred" shops are not for the benefit of you, the consumer. They are strictly a way for the insurer to maintain control of the repairs to keep their costs to a minimum to maximize their profits. Through these agreements, many claims are paid far less than what you, the insured, are contractually owed.
DRP shops are "graded" on quickness of repair and how cost effective the repairs are done; quality too often takes a back seat in these situations. Insurance Companies are not car repair professionals!
Would you want your vehicle repairs potentially compromised because the shop had to rush the job, otherwise they suffer a "failing grade" and pay for a portion of your car rental. Is this the motivation you want your repairer to use when your car is in the shop? Safe and proper repairs should be the primary motivation of all shops.
You will find that insurers are not warrantying anything. While they may claim to warranty non-factory, junkyard, and re-manufactured parts, ask them how they can warranty your safety in the meantime while you drive down the freeway at 70 mph with junkyard suspension parts under your vehicle! A warranty is no good if you are injured, or worse.