Well, you can put catchas in case you doubt there is a bot activity. They also have so many phone number and email they can use that to do additional checks.

Well, you can put catchas in case you doubt there is a bot activity. They also have so many phone number and email they can use that to do additional checks. They you can use the network effect: bots usually have something in commons: topics, likes, ip, followers... If you have millions at your disposal, something can be done. They are not, so I'm more encline to assume there is benefit for them to avoid doing so.