Scubabros is just giving the standard liability argument. SP has been using that one for years. The reality is that for the user, as long as quality parts are used, there's zero difference. For a dive shop in business, there are financial issues, like being hung out to dry by the manufacturer that provides your inventory because you didn't follow their agreement. We do live in a litigious society, and one that wrongly believes that scuba regulators are somehow "life support." Of course, anyone with a brain and some decent scuba training understands that ALL safe diving practices involve contingency for equipment failure and OOA scenarios. So nobody has ever been killed because their regulator failed. If this were widely understood, the liability issue with servicing regulators would be minimal.
Guess who's to blame for this? It's the scuba gear industry, that keeps waving this idiotic "life support" flag in order to sell more expensive regulators and control access to parts. And they brazenly do this while teaching, at the same shop by the same people, about air sharing, buddy system, CESA, etc....all things that clearly indicate that regulator failure is not life threatening.