Or hell, computers. Why is Apple allowed to have Apple stores in New Jersey, but Tesla is not allowed to have Tesla stores?
Don't think this isn't something every state legislator in every state is thinking about. But it's a hard sell to reverse the course of the river and keep your seat. With dealerships, they're already the established model and keeping the status quo is much less work.
In your example, states are actively trying to collect at least sales tax. New Jersey is no exception
http://www.northjersey.com/news/sales-tax-decision-could-be-...
That can be said to be true about everything. Why allow online software sales, or Amazon purchases? Force them to have local BNM shops.