OK, they have a few.
Translate the prices to USD and they are about 2x the price of an equivalent Triumph Classic so I doubt that a Triumph dealer in the US would carry them.
There is a great deal of startup cost. The local Triumph dealer opened a few years ago and had a showroom full of bikes, a fully stocked parts dept. and a service department ready to go at the grand opening. The owner and partners mortgaged everything they had to get going in a small warehouse facility, now they have a very large showroom with six brands. Today they have 195 bikes for sell of which 149 are new. None of the equivalent bikes of the six brands cost anywhere near as much as a 961. Just like with cars, dealers don't make much on selling the bikes, but the service, parts, and accessories do make a lot of money.
Norton is being smart to grow from home, IMHO. Then, IMHO, they need to get enough market share and volume to get the price down to something reasonable, especially for younger riders. The new Triumph 400 is likely to outsell the Rocket 3 by a LOT, especially in congested areas. Even though I could easily afford a 961, I definitely would not pay that much for the name!
Having lots of dealers in a place as small as England and having very few bikes to service is a good way for those dealers to fail unless they make their money elsewhere.