Discovery and Recommendation in those apps seem to be features, not the purpose of the app itself.

The purpose of the app is to sell ads via engagement, recommendation is at least a partial (majority?) driver of engagement, so it’s part and parcel of the purpose of the app.

People want what they’re providing, companies want to sell ads, and increase people’s tolerance of ads. Until the next platform without ads comes out (note - tiktok didn’t have ads almost at all for the first year)