cause someone went through some serious shit to invent this. it's a disk that you put the beer on and, i don't even know. watch the video.
all you do is simply plug in the surger, put a little tap water on the metal plate, pour your can of guinness, which has been chilled in the fridge for the recommended 3 hours, at the recommended 45 degree angle, it's as simple as that!
(paraphrased, but close)
so guess what, guinness drinkers, you've poured yourself one pint (that's still not as good as an irish pub pull) and i've downed 3 pbr's. it's as simple as that!