Centralisation of process isn't just about dollars for data. Yes, for the business model to work, the company has to gather a lot of data that it can look at all at once. But that's perfectly possible to do through a network of services, even services you don't own. See ad-servers.
Centralisation on the product level – that is, all activity happens on this particular piece of user facing software – is also a function of ease of use. If a thing is being accomplished by a distributed set of different interfaces, each with their own rules of the road, then there's significant pain for the end user in navigating all of that. In this way, good UX is naturally monopolistic.
Disclaimer: I briefly worked for Academia.edu a few years back.
Centralisation on the product level – that is, all activity happens on this particular piece of user facing software – is also a function of ease of use. If a thing is being accomplished by a distributed set of different interfaces, each with their own rules of the road, then there's significant pain for the end user in navigating all of that. In this way, good UX is naturally monopolistic.
Disclaimer: I briefly worked for Academia.edu a few years back.