Your last sentence is and always has been the key for me. In most realms of disability services and from the education side of things (Special Education) the mindset is to function in the realm of least restrictive environment. In simple terms, that is to provide accommodations/modifications that allow the person with the disability to function as normally as possible with their peers, with as few restrictions as possible.
DAS to me from education mindset would be like giving every one who qualifies Full-time Support, which is the highest level you can get. Normally you start with the lowest level of service and work your way up to someone needing the highest level of service. In Disney's case they've already started at arguably the highest level of service (short of saying you can come to the front of the line right now).
Unfortunately, when you start there, it is hard to go backwards, which I imagine is what's causing a lot of the frustration for some people. Even though other accommodations could work, might actually be very reasonable, once you've had a higher level of service, and know it works for you, and know it's made you have a successful park experience, it's hard to want to try something less than what you know can/does work.