Real answer: Because ghost's aren't real, of course.
Hippie bullshit answer: Because ghost's have unfinished business, and since dinosaurs weren't sentient in the way humans are, they won't have any unfinished business.
Real answer: Because ghost's aren't real, of course.
Hippie bullshit answer: Because ghost's have unfinished business, and since dinosaurs weren't sentient in the way humans are, they won't have any unfinished business.