I am working on a product which requires people to scan QR codes to access features. It would have been better if any Phone out there could scan QR codes without installing any other scanner app.
My Moto X (2015) camera app automatically scans not only QR and bar codes but also scans and OCR's business cards. This might also be true on recent Nexus devices though I don't have one so can't say for sure.
Maybe because it might make it impossible to photograph close-ups of QR codes without actually scanning them?
In the sense that making the default camera app into a QR scanner entails that in a certain subset of use-cases it becomes impossible to take a photograph and not undertake a scan.
Whether this is considered an issue by those studying such matters is unknown to me; I'm just speculating wildly.
Moto X camera app has a neat solution to this. When it detects a business card or a QR/bar code, it shows an on screen indication of this instead of changing mode. You can continue to take a picture and/or handle the on-screen notification in whatever combination you desire.
I agree it would be great if smartphones had a QR code scanner built-in. It would save lots of code duplication for basic tasks.
On the other hand, you would have to trust that native app being the 'man in the middle' for the data scanned.