Collection - Iterator.remove() vs Collection.remove()

As per Sun ,

"Iterator.remove is the only safe way to modify a collection during iteration; the behavior is unspecified if the underlying collection is modified in any other way while the iteration is in progress."

I have two questions :

1. What makes this operation "Iterator.remove()" stable than the others ?
2. Why did they provide a "Collection.remove()" method if it will not be useful in most of the use-cases?