The distinction does seem a bit arbitrary, but I think it's the difference between being able to pick what you watch on demand, and having a lot of channels that are just playing whatever.

Actually Disney’s CEO touched about that during that last town hall. They release the shows both on traditional TV and streaming. They realized that the demographics using either platforms don’t overlap so they decided to continue with a parallel release separately to increase their reach. (I was a camera operator filming the event, I’m not a Disney employee, nor do I support any of their opinions)

They mostly are, or owned by the same companies. The consumer cable companies also deliver Internet access for streaming so they're still getting paid.

Because content owners don't need cable providers to stream over the internet.

HBO doesn't need Comcast for streaming, they can (and do) stream themselves with HBO Go.