They are all over the place here. Scrapping is a saturated industry in this area.
Some are totally legit, some are supporting a meth or crack habit.
One guy here has his AL "junk dealer's license" # (an actual thing) and insurance # on his truck. Most of the others don't, but seem legit enough. You see them in the same areas, and without suspicious goods like lots of HVAC components or lots of wire. What they have looks like actual discarded junk. They wouldn't be sticking to the same areas if they were problematic.
There are the thieves still. The state passed some laws preventing it, and some yards do a good job of cracking down themselves, but HVAC and plumbing that is an easy target will still get snatched.
In the city, homeless people do a lot of the scavenging. Generally it's not a problem, but sometimes it is. One night I saw a guy digging through my building's dumpster. Obviously homeless. I didn't think anything of it as it's common and let him be. The next morning when I came out, stuff that had been in the dumpster was strewn all over the parking lot. Nice. That has only happened once though, and I see people in the dumpster about once a week or more. Everyone ranging from homeless people on foot, to guys in pickups/vans, to a guy in a mid 2000s Accord digging for electronics.
As long as they aren't stealing or making a mess, it's all good in my book. I've scrapped plenty of things myself. I don't go dumpster diving, but my boss and friends know I will make unwanted metal go away. Right now there are A/C components for a Jeep Cherokee laying in the bed of my truck in fact.