On the part where you say the cars didn't need totaled, The cost of the repairs have exceeded the threshold whatever it may be. Like you said used to be 75% sometimes less as they look at other factors such as how long the customer will be in a rental. I've seen customer attitude play a role as well. When a person's car gets hit sometimes there is absolutely nothing you can do to satisfy them because of the "it's been wrecked stigma"
Ins co's are not in the habit of writing parts a car doesn't need. With rebuilds, it becomes about what can I repair/save and put the money in my pocket. Not saying every shop will hack one together, but it happens. All said and done you selling a car with the "rebuilt" stigma at a discount to a more educated consumer these days. You can wrap up a bunch of your own money in finished cars that don't go anywhere fast. Alot of times the only way to get the cars is that the owner gets first dibs on the buyback,and I have got a few this way, but most don't understand and take the check from ins co even after offering them a premium. Most salvage yards build cars, so everything that hits the public has been gone over as to feasability. As discussed earlier the shop these cars are sitting in alot of times can't even bid on them. You end up with a lot more time involved in these cars also, going to auctions, chasing parts, dealing with tire kickers etc on top of doing the repairs. Go do your local auction circuit. I would start there if your really interested in this. It doesn't take long to figure out alot of cars run the circle until unsuspecting buys it. Inspections can be limited and can make or break you. Do your reseach. been there done this, it wasn't for me.