Truth. Impact sockets typically have a matte black finish (does the chroming process affect the strength?) and if you were going to be concerned about a damaged socket, it’d be with impacts.
Believe me, the mechanics pay the same crazy high price as everyone. Or more likely, they finance it.
For tight spaces there are extensions, nut drivers (some with T-shaped handles for more torque), and flexible adapters. One of these will initially be needed to loosen the fastener. Using that tool for an additional few strokes until you are SURE it’s finger loose completely removes any need for the special sockets you desire. Wearing the right kind of gloves will also go a long way.
I could believe a safety issue is the reason they don’t do it. Would the knurling make the sockets more likely to crack? Could those indentations make it easier for cracks to form and follow those lines? It would explain why those Craftsman ones have such a tiny band of texture.
No, it makes it harder to see a crack.
I have all different length extensions that have a rough surface pressed in, the rough surface does help a lot but you really don’t need it directly on the socket.