It’s not a secret that the native camera app works this way. It’s been well documented.
Many of the 3rd party camera apps that offer manual controls allow you to chose which cam to use for a photo.
Although I never thought I would go with a Plus sized phone, I did read many reviews and saw many Youtube videos on how the cameras fare. I did not recall any of them pointing out that it only engages the tele camera under what the phone thinks is ideal conditions.
Without optical stabilization, the images from the wide angle lens will often be better unless you’re in daylight-like lighting conditions. So the bias for wide angle is pretty severe in anything less than daylight.
This also means that if you have very steady hands, or are using a stand of some type, that the camera app will often be making the wrong choice and you’ll be better off with a 3rd party app.
Now, if you test the stock camera app in daylight and it still doesn’t use the telephoto camera you may actually have a hardware issue of some sort.
What is funny is when I was messing with it last night, pointing the camera directly into the 100W light bulb, it still wouldn't engage the tele camera. Just now, I'm pointing it into my monitor and it went straight to the tele camera. Yesterday I was pointing out the window under full daylight and it did not engage the tele camera. So it seems to have a mind of its own, and given that I can choose between the wide and tele camera at will with a 3rd party camera app, hardware issue can be ruled out.
I kind of get why Apple implemented it this way, so that they don't get complaints over dim and/or blurry shots under low light conditions. I would've at least appreciated an indicator telling me when it's using the software zoom so that I can take action to avoid it. I know perfectly well how to operate a camera, having used to be a camera nut myself. However, I like the simplicity of the stock camera app. Just look at the clutter that is the 645 Pro camera app UI. I know there's a price to be paid for simplicity, but I'm still surprised it is forcing the use of software zoom.
In my book, using digital zoom is as big a sin as shooting portrait videos, neither of which I'll ever do lol. I can decide for myself when the tele camera is not ideal, and choose to use the wide camera myself and crop it later on, APPLE
