They can potentially become a blight. I'm not talking about a single classic car you're restoring, I'm talking about 3+ vehicles, some parked on driveway, others on the grass. They're homes for vermin and other animals, they're a disaster aesthetically and probably dangerous to kids in the neighborhood (sometimes they're on jack stands). They're often accompanied by stacks of tires and other debris.

I've lived off-grid in the desert, and I've seen certain people become 'garbage collectors' - a few cars turns into 20+, with all the associated junk. In the desert, nobody really cares - but you'd be crazy to move in next to one of those junk yards.

It's not going to ruin anyone's life, but it's definitely not nice. It depends on the community and circumstances I suppose.