exactly. you yourself just described how complex it is. you need to:
-unlock the phone
-locate the app (camera or specialized app)
-open the app
-if it's camera, make sure it's in the right mode (not video/selfie etc.)
-carefully aim at QR code
-tap to scan
it's a labor-intensive cumbersome process that is also utterly boring. this process cannot even be called "scanning".
true efficient scanning of QR code would look like this:
-unlock the phone
-pass the phone over the QR code
that's it.
until then QR codes will never become popular.