In layered application architecture there's a fundamental rule that says that you must never bypass a layer. If you query your repository straight from your controller, you would be violating that rule.
So what? you may say. What if the service layer adds no value? Well, it might in the future...
You can choose to break the rule, but then it wouldn't be a layered application any more. That may be okay too - there are other good (even better) application architectures available, but I think that first you should make a decision regarding the overall architecture, and then you stick with that decision. Otherwise you'll end up with spaghetti code - we call it lasagna when it's a layered application :)
