No typically the reason is if a RSP did the install they purchased them much cheaper than a new one.
my old RSP from years back before that crap hole ViaSat bought them out did that for years, the owner even told us he did.
We would have reman receivers all over the place and rarely got a new one to push out unless it was something newly released.
You were better off telling customers at that point to have Dish send them a replacement for failure issues a few weeks after we were gone to avoid the TC so they could get a new one sent via the mail and send back the reman.
Stock being low maybe but if it was an RSP doing the install the above what I stated was likely the reason.
That's not how it works for us. We get whatever the distributor has in stock whether it's new or refurbs and they're all the same price.