for me the camera is one major reason to upgrade every 1.5-2 years. But I buy a phone(asus) that is at least 50% cheaper than most of the high end phones so I figure I'm coming out ahead. They probably have better cameras but mine has been good enough until the next refresh cycle
For me, cameras have become good enough in around 2014, before then, smartphones cameras tended to turn low light pictures into a blurry mess.
Things will always improve, but for cameras, we are getting to the point where if your smartphone camera isn't good enough for you, you are probably at least an enthusiast and you probably want to get a real camera.
Since then, I've seen absolutely no game changing improvement.
