Yeah. I get that. And two 17 year olds can be a "couple". But Disney isn't going to build an entire resort and then put a "Children not welcome" sign on it. Even V&A has a cut-off at 10 years old. The
Disney Cruise ships have 'adult only" dining options, but that is a very small part of very large ships. I can see having "adult only" pools, spas or lounges. But a 1,000 room resort? You won't see it.
"Adult only" is a very tough thing to manage and why would Disney want the headaches. For example, Disney put in the "adult only" restaurants on the cruise ships, but that is not always a good fit. I can understand wanting a restaurant with no kid's menu and screaming 5 year olds. But why can't a family with two parents and a 17 year old and a 15 year old dine there? The teenage children are far closer to being adults than they are to being 5. Issues like this are a constant cause of strife and Disney doesn't need the headache.