A quick search on "finn. no" will show that there are approximately 1,500 BMW 5-series models for sale in Norway. Of 1,500 has 600 towing hitch! You can even find the BMW M5 with towing hitch!
This gets a little guesswork, but I think Tesla could have sold very!! much better in Norway if they provide towing hitch on Model S. (Because Tesla Model S is an alternative to "all" family cars in Norway, because of no tax on electric cars in Norway)
So I really can not understand why Tesla does not provide towing hitch on Model S, at least in Norway, unless they do not want to see the Model S with a nice boat or caravan hanging behind :)