A lot of things we do with cars make no economic sense. Buying a brand new car makes no economic sense. I am pretty sure I have more in my Healey (I stopped counting) than it will ever be worth in my lifetime.
People (including my wife) have asked why I restored a car with so many needs (broken frame, toasted engine, ratty interior). In hindsight it would have been better to get a restored car but I was uninformed, naive, and cheap. Once it was mine I felt I had 3 choices: dump it and lose money (smart choice!!), keep it and just fix what is broken (very hard to do), and total restoration. I started with choice #2 and ended with #3.
Why didn't I dump it? I hate quitting anything and I was embarrassed that I had made a mistake. I also felt I had an obligation to the car to fix it. Nobody understands this except some car people. It's like when you start feeding a lost puppy. Hey buddy, it's yours now.
Now the good side (what I tell my wife now). I've got a good car. It is just the way I want it. We enjoy driving it and plan to keep it for some time. And the market has risen in 20 years to cover some of the sunk cost. So, was buying the car a good decision? I guess it depends on what you value. In a monetary sense, no. In experience, I have great stories to tell, I know every inch of the car, and there is a special pleasure in driving a car that you have rescued.
So why buy a rusty wreck? Unless you have a special vision, loads of excess cash, and lots of time you shouldn't. But if you do, why not?