I think you're trying maybe a little too hard to see this from a product/horses-for-courses angle, but the subway analogy doesn't make sense. Subways have very practical and technical reasons to run on their tracks and exclusively operated by professionals. AFAIK there's no subway out there that isn't a closed ecosystem, and it likely doesn't bring any benefit to their passengers.

OTOH we know tablets, smartphones and cars can operate in an open manner, and their users benefit from this, so Apple choosing not to make such tablets and phones is similar to cars that could operate on any road and fed any brand oil, but Apple choosing not to.