I guess if the serial number is missing or etched off, that’s a good reason not to show the rear
Seller Listing Pet Peeve
When I'm viewing for sale ads one of the first things I look for are the connections the particular piece of equipment require or can accommodate.
The latest was a DAC that had many photos of the top, sides, front, even different angles of the same view, but not a single photo of the rear. Yeah, I know I can look it up if I'm that interested but the seller could make that point easy on me.
To me it is critical to understand the options/limitations of a piece of equipment from the very start whether it is an amp, preamp, speakers, DAC, etc.
OK, rant off.