I used the 'notes' app on my 5s for about 6 months before I realised it was secretly sending everything I typed to my Gmail account. Why is this even a feature

I used the 'notes' app on my 5s for about 6 months before I realised it was secretly sending everything I typed to my Gmail account. Why is this even a feature at all, let alone a default one? Why didn't my phone notify me that this was happening? I've since disabled it (and scrubbed the emails), but it's still the biggest breach of privacy I've ever experienced on a device. I'm still not sure who to blame, either. Apple? Google? Or me, for assuming that my note-taking app wasn't secretly broadcasting all of my keystrokes online?