Why does ObservableCollection not support bulk changes?

Question

What are the potential problems caused by an ObservableCollection supporting operations like AddRange or RemoveRange? There must be a

Answer 1

There must be a reason why Microsoft didn't provide them

They do not provide every possible piece of functionality, it's (also) a cost vs. demand thing.

You could implement your own collection that supports bulk operations and implements INotifyCollectionChanged.

Yes. And when you do, you'll find that the collection will have to make choices about how/when to propagate those changes. I never tried but I imagine there are some trade-offs that the View or ViewModel can make better decisions about than a reusable collection.