You Probably Don’t Have Much 4k Content Yet
The big selling point of the latest Apple TV is 4K compatibility. This can vary between users, but most people don’t have enough 4K content yet to justify making this upgrade. Remember, only limited modes and certain channels have 4K options when streaming, and you have to buy 4K/UHD movies if you want them in the highest resolution. You also need a 4K TV, of course. That limits the usefulness of this feature unless you’re already heavily invested in 4K.
The exception here, of course, is if you are already heavily invested in iTunes content. iTunes offers free 4K upgrades for all of its movies, for example, and the Apple TV 4K also offers nice HDR options to make sure that content interacts well with your TV.