You see family and friends for about 3 hours, why play video games ignoring them whilst you can actually be hanging out with them? Also, you'll need to buy a new one if you want to upgrade. Laptops overheat, as mentioned before, too. You'll need a USB mouse to play comfortably, and even then playing at a desk is yourbest choice.
You don't need to buy a new one to upgrade. Although it's pretty hard to do, you can replace graphics cards in laptops. But on the downside, sometimes you will need to replace the whole motherboard as well. But in the end, Desktop is superior. :/