I sit at an Apple desktop (macbook pro with 2 apple monitors) for most of my day so I can use my giant screen to design interfaces and I'm not cramped into a laptop's tiny 13 inch screen. The last office of about 5,000 devs and designers that I worked at had desktops with monitors. No one worked on laptops except a few people here and there.

I would lose HOURS of productivity per week if I were not on a dual screen set up. It's just better for what I do.

That being said, if I need to go mobile, which I normally don't I use my macbook. I think I've disconnected my macbook from my monitors probably 2 times in the last 2 years.