So using your logic......
Then iphone buying public doesn't need 3D Touch or even Touch ID....the the models that didn't have those features sold extremely well. So I guess going forward the iphone does not need any additional features because it is selling so well as it is. See how flawed that logic is? The iphone 6 didn't need a larger screen then huh?
No one is saying the lack of a notification light is hurting iphone sales. I am an iphone buyer and would love to have a notification light.
Why would you be against a useful feature? It makes no senses to me.
If you have no use for it.....great. But others would love to have the feature.
Actually my logic is: it is completely up to Apple.
Now regarding the notification light, I use to want that feature, but ever since purchasing an Apple Watch, it no longer bothers me. The Apple Watch acts as a notification light and so much more.
If it bothers you that much try an Apple Watch. You don't really have many alternatives.