Assisted Living facilities do have married couples living in them where both due to age or disabilities can no longer care for themselves fully. It doesn't mean they need 24/7 supervision just that things like meals etc need to be provided.
I married my girlfriend 28 years ago who is a quadriplegic. Ten years into our marriage I got hit with a disabling condition. Thankfully though I can still take care of our basic needs including cooking. What 5-10 years down the road will bring we don't know. If/when time comes we can no longer live alone what then? BTW both of us are former health care services related workers. Things have changed drastically in the past decade or so and it sounds like New York is behind the curve. They could likely get by OK in a group home for disabled married couples is what I'm saying. Two disabled spouses is not all that uncommon.
I think you’re right about services for disabled couples.
But I suspect for many group homes for the mentally retarded, things are much easier to handle if they are single-sex.
It’s good to have a variety of things for a variety of people, but not to force everything to be for everyone.