I don't really know Virginia geography, but here's my guess on locations.

-- Not in Northern Virginia: a NIMBY decision for the affluent suburbs of Wash DC.

-- Bristol & Danville: on the southern border. Draws from No.Carolina & Tennessee. Out-of-state customers are especially sweet for tax revenues (See Nevada vs. California, etc.)

-- Portsmouth & Norfolk: are these natural tourist destinations for going to the beach, etc.? Fits in with leisure/hospitality options.

-- Richmond: as the state capitol, maybe a tourism play, or just economic development. Bringing home some bacon for the locals?

It wouldn't surprise me to find that these locations correlate to proponent's districts in the state legislature. Bragging about creating jobs & infusing gambling tax revenue into the local economies if what drives a lot of these decisions.

Just speculating on this, but as tobacco use (and associated state revenues) has declined over the decades, replacing those tax revenues with another vice tax may be attractive to the state legislators. Sounds cynical, but ...