What you don't realise is that you don't just code something, check it on your friend's device and release. There are issues with the UI that must be tested ( localisation, built-in themes, consistency, font sizes, et.c.), issues with the firmware upgrades and existing messages, issues with functionality itself so on and so forth. I could probably come up with a substantial set of tests even without knowing the internals

QA work is not test a few times and throw out to the wild.