In the iTunes Store you mean? There are - they're gradually moving from 720p to 1080p. Nevertheless, I wouldn't bother with the (comparatively) low-quality iTunes Store movies myself. Rip your own BD's for the best quality.
Here in germany you can only rent 1080p on the ATV3.
All movies you might buy in iTunes are still 720p even though they are available as 1080p on the ATV.
I've watched plenty of 1080p movies from the iTunes Store and I cannot tell the difference between them and BD videos. Both are remarkably great quality.
The are many 1080P movies to buy and rent on Apple TV 3.
I'm not sure but I think there might be an option that allows you to choose the default quality for movies you rent / buy (like in iTunes where you can default to either 720P or 1080P downloads). Maybe have a look in the options and see if there's something you've accidentally changed.
In the iTunes Store you mean? There are - they're gradually moving from 720p to 1080p. Nevertheless, I wouldn't bother with the (comparatively) low-quality iTunes Store movies myself. Rip your own BD's for the best quality.