SimonG: How many people are actually going offline nowadays? Honestly. The last time my computer was on but offline was when I had a dialup.
rampancy: Portable users, for one. We're still a long way away from having ubiquitous free/affordable public WiFi, and internet over 3G is still untenable; even in South Korea tethering may be subject to extra/excessive billing even though your contract may be for unlimited data. Yes, the buses and subway trains in Korea, and even the KTX now has WiFi, (and some US/Eur air carriers now offer in-flight WiFi) but in my experience they're not the most reliable connections in the world, and aren't the greatest at handling the gigabytes of data Steam usually asks for when it randomly decides to update itself/your games.
But will you be playing Sim City on the Subway? Games like that aren't meant to be played "mobile". Saying that laptops as a whole are not meant as gaming plattforms is probably going to far, but I don't complain that my netbook can't run games with no resolution smaller than 1024x786.
For me, a Laptop is a tool in the first place and an entertainment device secondly. My "big boy" is my TV/Console/Stereo and general entertainment platform, and he is only moving when I'm "moving".