There is nothing to say that a company must derive their revenues from a single source. It has always been like that, or at least it has been like that for a very long time. Newspapers derive their revenue from both sales to readers and sales of advertising. If you subscribe, they also sell the subscriber data. The same thing can be said of warranty cards. You don't see them as much these days since it turns out to be far more reliable to force people to register their product when they first turn it on, but it was always a way to get marketing (and marketable) data.
There is nothing to say that a company must derive their revenues from a single source. It has always been like that, or at least it has been like that for a very long time. Newspapers derive their revenue from both sales to readers and sales of advertising. If you subscribe, they also sell the subscriber data. The same thing can be said of warranty cards. You don't see them as much these days since it turns out to be far more reliable to force people to register their product when they first turn it on, but it was always a way to get marketing (and marketable) data.