This is the problem with any fitness app.

They either need to show you ads, charge you for premium for services that used to be free making your free tier functionally useless (looking at you, MFP who gated barcode scanning behind their honestly ludicrously priced subscription), or sell your data, and they often do all three.

The entire industry is like this, and honestly an app that charges one time and fucks off would be ideal but given the amount you'd probably need to charge as a one off (or for major upgrades) most consumers would rather have the slow bleed of $10/mo than $25 one time.