I think they are popular mainly within certain socio-economic/cultural circles. They started getting used more once a few celebrities started using them. I imagine they will rise some more, but I don't really expect them to get much more popular.
Don't get hung up on numbers. It could be that
Hazel and
Jasper don't even make the top 1000 in your area. They sure aren't used here. I can think of only one young
Hazel that I ever heard of. Her name is
Alexis Hazel, she's about ten, and
Hazel is after her grandmother or great-grandmother. She is not actually called
Hazel.