Ummm Dale...the car manufacturers DO make crash (replacement) parts, but these days they RARELY get used on vehicles over 1 or 2 years old. The aftermarket, usually inferior-fitting parts, are MANDATORY...REQUIRED by MOST insurance companies on repairs to less-than-new vehicles as a cost-saving measure (or junkyard "LKQ" parts on even older vehicles). It's NOT that the car builders don't want to be in the repair parts market, but that the insurance companies have driven them out of it.
And ummm... I've been in the 1:1 body-repair business and I'm not just giving an uninformed opinion.