If I had a Linux laptop, an extraordinary amount of my time would be spent trying to make it work. Wireless breaks, sound breaks, upgrades break everything. I would have to spend a serious amount of time and research finding a laptop that had good Linux support... regardless I would still probably have to spend hours trying to get the sound or the wireless or sleep or some feature or another to work properly.
OS X just gets out of the way. I have never had to put any work into making the graphics card work or making sound work or making the network work or fixing boot... you get the picture.
If I'm using Linux on a laptop to do any sort of work, a sizable portion of the work becomes keeping Linux working on the laptop and I don't want that.