Declaring an emergency is a way to get from ATC what you want / need. It also gets you attention. They did the right thing, not getting cooperation from ATC for whatever reasons. If you don't get it, demand it.
Our airline preaches to declare emergency if we think we need it. If it turns out we don't, you can always downgrade it to a pan-pan.
Better safe than sorry - declaring an emergency is mostly paper work. And who doesn't love that, right?