These companies are mostly platform businesses that facilitate interactions between different types of users of their platform. They have very large user bases, benefiting from strong network effects that can make it hard for competitors. Data analysis is part of their DNA and they have become increasingly effective at commercialising the value of data they collect and analyse.
Providing additional services, such as payments, also reduces the need for users to ‘leave’ the platform. So there are complex issues to be worked through here. One of these is the terms of access to the platform and whether the platform requires that payments be processed by the platform’s own payment system.