It's logical. I tried to sell some scrap iron that had accumulated in back of the garage over the years at the local salvage yard. I had to produce a picture ID before I could unload it.
Things just don't make sense.
Probably because thieves are more entrepreneurial all the time. Pipe, especially copper, and wiring are disappearing even from houses where people were away for the weekend. Also construction sites and abandoned or vacant buildings. And it's not always the usual suspects. Good for the yard.