> Tie-in sales between software and services

Look at it this way: the service that you're accessing is really a (primarily desired) side-effect of the software. So re subscriptions, what they're actually providing are the apps (web, desktop, etc), and the apps use their service to aid the fulfillment of their functionality. Those wanting direct access to the internal service can get an API key for that purpose. That's just how their product offering is structured.