I find it interesting to do myself. If you don't have a background in biology, you can learn yourself easily via the internet. Look up pics of necroscopies, and you'll get a good idea of what healthy tissues look like. When you open your animal up, you can often see somethign obviiously wrong - impactions and some digestive issues are easy to spot even without any prior knowledge. Some parasites can kill animals outright, husbandry can cause problem sin the long-term that might be obvious on the inside (fat lizards look really fat on the inside), Infections often are easy to spot if you have a pic of a good organ to compare it too.
In genreal, it's a good way to learn abotu the animals.