There is one essential difference between a laptop and a desktop: mobility. And there are two things that together make this freedom possible: a battery and a wireless card. Without a battery, you are very limited in going places and have no real need for a wireless connection, and without a wireless card you can go as you please but might as well be stuck within cable range of your router.
Having owned computers that were lacking in either one or the other, I have learned this very well.
(Sorry if you were looking for something deeper, that's all for today. Musings range the spectrum from profound to superficial)