I feel like they do this a lot with main characters not part of the Core Four, though, and especially with their non-white characters. They won't really bother to develop them. Now, recurring characters, sure, they'll throw together some half-assed backstory for them and call it a day. But they really stopped developing their other main characters since season 2. Just because they show up onscreen and occasionally get a subplot, it doesn't mean they're properly developed. Or maybe they're getting development, just poor development.
It's a shame, because Erinn Westbrook is a great actress