If you look at Apple's profits - it's about evenly split between 'Services' ( like music and app sales etc ) and hardware.
Now hardware gross revenue is about 3x the services - but the profit margin is much higher on services.
Apple don't break out the numbers so it's difficult to know how much of that service revenue is tied to people owning Apple hardware and how much is independent ( like Apple Music or Apple TV ).
yeah I think the key point is in your last sentence - maybe some people would buy Apple Music/TV without an iphone or an AppleTV? I don't think anyone would buy icloud without the hardware though. And presumably they're bundling applecare in the "services" as well :)