I think developers would get annoyed with having to add another double vertical live tile to their apps. And I cant really see any other apps that a vertical tile would be useful for expect for the calendar as displayed. I can't personally think of why you would use the start screen horizontally, I know I wouldn't, but to each their own i guess.
Many devs don't even have the 3 tile sizes that are currently available, so I don't think it'll be an issue anyway. For example, many apps don't have a double-wide tile, but not all apps need it, so it won't be available anyway. For devs that want to make a double-LONG tile, they should be able to. Plus, I'm sure they are going to introduce even more sizes when 1080p screens available (also with Windows Blue the double-wide-double-long (i.e. large square) tile). Devs that are interested will come up with interesting tile designs if the options are available.
Also - that's fine that you don't have a use for it, but many other people do. For example, when you're watching a video and instead of having to rotate your phone, you can continue using it in horizontal mode. People have their preferences, so nothing wrong with options.