With the correct care, and shipment from both the store to your house, aquariums can come home without any damage. However fish, gravel, or sometimes even the wrong placement of decorations can cause for scratches to appear out of nowhere. Have you ever had any of your tanks have any after they were setup, and what did you do?
Recently my 55 gallon has some pretty bad front-facing scratches which are highly noticeable. Thankfully, it is not too deep and is on the inside (better than being on the outside), however it does make me question the overall integrity of the glass and also makes me want to empty it so I can spin it around to a clean non-damaged side. If there were anymore, or it was any worse I'm pretty sure that I would just go out and get a new tank to avoid the mess of the glass getting damaged more, or the scratches turning into cracks which no aquarium owner ever wants.