[soundman98]

Most of it comes down to insurance regulations and requirements. Insurance says the oems method is the only acceptable method.

I just worked is house today that had work obviously done by a contractor. On the surface, it was correct, but once the wall was opened, fittings were missing, and they hodge podged connections to make everything appear to work.

You're making a lot of assumptions that the person doing the work is qualified enough to make alterations to the repair process. In that previous body shop link, someone died in large part because of what could easily be considered a simple change in installation procedure. But it had serious ramifications in the structural integrity of the vehicle chassis that they didn't account for.