That's a good question. Personally, I don't know how this will help us understand why dinosaurs went extinct, but according to the latest findings in the journal Proceedings of the National Academy of Sciences, because dinosaurs took so long to hatch, they were more vulnerable to being eaten, while parents risked starvation protecting them. Researchers have found growth markers called von Ebner lines in the teeth of dinosaur embryos which, I assume, can tell them roughly how long the embryos were in the eggs before hatching.