In certain situations it makes sense.
I bought one of the Asus gamer laptops back in 2009 because I knew I would be doing a lot of long-term, international traveling in the near future but I wanted to be able to game no matter where I was. It's the only thing that made a shitty week in Istanbul bearable, and it kept me sane when I was out in the boon docks in some third world shit hole without anything else to do. As an aside, Steam also makes this really great because you can just preload a ton of games, switch it into offline mode, and you've got an enormous gaming library at your finger tips no matter where you are.
If you're just going to move from your couch to your bed to your desk then I agree it's stupid to buy a gaming laptop. Since switching to a desktop pc last month I do find myself missing being able to lay in bed and watch a movie, or put my laptop on the table while I'm cooking dinner, but I figure that's a job for tablets nowadays, anyway.