Most elements of our digital lives (e.g. apps) only exist within themselves and seldom work together. Because workflows are more useful than point solutions that leaves users with the burden of getting things to work together, humans are the interop layer.
For example, a hypothetical product like a spatial note-taking app would require that participation across email, browsers, and even the operating system. However, this is extremely unlikely to be done well because interoperability is stunted due to lack of monetary incentives for cooperation between apps.