Are you a greedy little fucker? Does your app have proprietary data in it? Are you building a walled garden full of weeds? Stop. Stop building apps that are hoarding my data. We have standard formats, let me export my data. Don't build apps that delete my health data from my phone when I delete your app.
You don't need to reinvent the wheel to build a todo app or a note taking app, just let me export a text file if you're so lazy about building something structured. Just don't build stingy apps that keep my data locked in. Are you being pressured by your MBA colleagues to create vendor lock-ins? Tell them no, it's not worth it. We as users need to stop using apps that don't support standardized formats.
Most of the data in apps these days is text and/or some variations of key/value pairs, just let me export it as a json, xml, or csv file. For the other files, images and videos, just let me download it.
Stop building apps that hoard user data for no good reason.