For the same reason I don't play Minecraft. They are both objective-less time sinks.
Now before everyone gets on my ass about it... Sure Skyrim does have a story, and quests and objectives and all that happy horseshit. But if you plow straight through that you end up with the sort of empty feeling that you've missed most of the game because you wanted to see the plot.
On the other side of that coin: The second you stop paying attention to the story and go off on your own you get so bogged down in side quests and exploration that by the time you're ready to go back to the story line you're so far out of the proverbial loop that you may as well just start the whole damned thing over again to get a rehash on the plot.
Then you have all the crafting and mining and skills that do fuck all for the story line and just exist as an artificial way to inflate playtime and make you think that the game is engaging you just because it's taking you longer to beat. It's not taking longer to beat, tard boy. You're just standing in one spot longer and watching an animation of some asshole swinging a pickaxe to obtain ore that you're NEVER going to use because it's too heavy to carry around.
Then there the skill trees. I watched a friend of mine start the game over 6 times because he had (in his words, not mine) "fucked up my skills and got stuck." And that got me to thinking that if one of the top selling points of this game was user-chosen level progression paths, then they fucked that up royally. If you can get irrevocably trapped someplace because you lack the skills to free yourself then they are locking you into doing things their way anyway and all their customization options are just for show. Sure, it offers a level of realism to in-game situations based on your skills, but to me that seems TOO real. I play video games to escape the harsh reality of the world, not be reminded of it at every turn.
The Elder Scrolls series takes everything I hate about Minecraft and MMOs and rolls them in a little package that they want me to pay $60 US for. Thanks. No.