D'oh. This'll teach you not to have theft coverage.
It's a sucky situation and, despite that "theft coverage" comment, I feel for you.
As for the reason? Older cars are easier to steal, having less anti-theft devices. They're cheaper to sell stolen, and cheaper than buying a "new" car. I could probably buy seven stolen 80s models for what it costs to get a newer vehicle.
Get the coverage next time.