Interesting. Yes, Cees, they keep being found--like there's no shortage of barns, or cars in them. They are still finding 300SLs in the same manner, a car considerably older and one they made very few of.
The reason why cars are left to sit like this for [insert # of years or decades] is that at the time they were rolled or driven in the barn, the then-owner made a decision that the cost to "deal with it" in any reasonable manner, was too much. Now, add those "x" numbers of years or decades, and the following has happened:
1. However "bad" it was, is now worse.
2. Some parts have gone NLA.
3. Other parts are unobtanium or priced like it.
Trust me, I know these things. My car was pretty much something akin to this. Not "found" in a barn, but in a garage. Not found, because it was never lost. Very rough in every possible metric when driven into the garage in 1985, and not uncovered from the tarp until 1999. See the photo when my car was dragged out of the garage. Yes, dragged as the brakes were frozen.
In 1999-2001, my car, in its first and initial restoration, took 1000 hours of direct labor, and probably $30K+ in parts...not including "sublet work" time and money such as chrome plating, instrument restoration, brake restoration, etc. I had a great restorer who allowed me to help. Labor was $45.00 per hour.
So, this car as presented is going to take a very long time, and a boatload of money to bring it back to life.