Why did Buffalo and Rochester dislike it so much?
I think there are some Indian casinos out there that probably didn't want the competition. Maybe they ran a vote no campaign to protect their racket.
That certainly doesn't explain Sullivan county.
Poor Manhattan, a tiny red island all by itself.
There does seem to be a correlation between voting for this and higher unemployment.
http://www.labor.ny.gov/stats/PDFs/ur_map.pdf
Sullivan County is very likely to get a new casino as part of the plan. It will be the closest full-service casino to New York City for a seven-year exclusive period before casinos can be built in the NYC metro. It had a lot to gain from the referendum passing.
One reason the Buffalo and Rochester areas likely voted against the referendum is that they're not going to get casinos under the proposal. They already have Indian casinos, which were protected. The areas expected to get one of the three casinos in the first round include the Southern Tier (Binghamton, Elmira), the Capital Region (Albany) and the Catskills (Sullivan or Ulster County).
