Some Tinder bots were designed to spam users to advertise some products. Some marketeers depend on spam to advertise their products or to bring traffic to their sites. See why do spammers spam.
Some bots are designed to scam users and to collect their credit card information or steal their money. In such a case, the bot tries to get the person to make a payment or to give up sensitive data. See why do people fall victims to scams.
People who promote illegal sites might use bots and other indirect methods to achieve their goals because they can't do that through the right channels due to the nature of their sites.
Some people theorize that some bots were created by competitors of Tinder in order to make the service worse and thus gain an advantage over it. See why Tinder became successful.
Some companies try to sell their products through bots. In such a case, the bot starts the conversation then tries to persuade the person to purchase something.
Many bots try to get people to visit a porn site. Because porn sites can hardly advertise directly on normal sites, they might have to use twisted ways to drive traffic.
Desperate affiliate marketers who don't know how to drive traffic properly might use scams or twisted methods in order to force people to check out their affiliate links.
Some Tinder bots try to persuade people to download a certain app and install it on their device. This is a cheap marketing method used by desperate marketers. See also Why Tinder relationship don't work.
Some bots try to get pictures from users or even force them to open webcams in order to be able to blackmail them later. The creator of the bot can use those pictures or videos to blackmail the person.