First, they do shady things with your data. Since I made a Tinder account I been getting constant ads for random dating sites. This have been going on for months. God knows how many companies now have my data.
Second, they employ dark patterns:
1) Easy account deletion. Why does that matter? Because they own nearly all dating sites. Including: "BlackPeopleMeet.com, Chemistry.com, Delightful, FriendScout24, HowAboutWe, Match.com, Meetic Group, OkCupid, OurTime, People Media, PlentyOfFish, Tinder, Twoo, Hinge" So, they don't care if they lose a user as long as they can shuffle them around.
2) They will keep a tab of the number of users who have like you. Then eventually that user will shown to you and you will swipe left or right. In that case the tab count will decrease. This is a complete scam. They would withhold these users to push to a pay subscription. Example: https://i.redd.it/e13yeek795x21.jpg . Moreover, most of these likes a bots and fake profiles.
3) Fake notifications: https://i.redd.it/r0lheira9rh31.jpg
4) Shadows-bans: I saw that my profile was getting no matches. So I made a new profile, ban! a match within minutes. Essentially they shadow ban users as a form of Neg.