Unless you've seen the recent Samuel Adams beer commercials. They actually explain their product. However, have you seen that new Pepsi commercial?
I wouldn't say there are never commercials aimed at information, but it is generally more effective and far more common to use commercials to simply try to attach a sort of positive feeling to a product. I wouldn't say "emotions are stronger" but that emotions are easier to manipulate, so often when you hear or see a stupid-funny joke in a beer commercial the company is trying to imbue a sort of positive 'good time' feeling into your impression of their product.
Another example is the viagra one where the cowboy in the truck gets stuck in mud then gets his horses from the trailer to pull the vehicle out. Everything from the characters take charge attitude and behavior to the dramatic music and, if I remember correctly, the "you're a man, take charge of your life" monolouge (rough estimation if I remember correctly) is designed to attached a positive 'manly' take charge feeling about using viagra.
In most cases actual information is less important in commercials. It's easier to manipulate an impulse than an intellect.