I still fail to see what's so hard to understand about it, or at least why people find it so hilarious.
How many people don't own a blanket for when it's cold. All this is, is a blanket with sleeves so you can hold your drink/remote/whatever without getting your entire arm cold.
Maybe it's because I live in New England where it averages about -5 overnight in Winter that I understand why you would want the sleeves.
Yes, wearing it at a sporting event is ridiculous, but some people do bring blankets when it's really cold/raining.