Laptop Notification Light - Why isn't this a real feature?

The image at left is a hacked, home-built feature added to a standard netbook, but it's pretty darn brilliant: a single tri-color LED, visible at all times (even when the laptop is closed) illuminates in different colors depending on whether there's activity on the user's email, IM, Twitter, or whatever. My question is, in an age of constant connectedness and instant updates, why isn't this a real product feature being offered by PC makers? Of all the lights that are visible on a laptop - power, hard drive access, wireless, bluetooth - why couldn't one be something just like this? It adds value, it would be cheap to implement, and could be as easy to use (for beginners) or customizable (for power users) as the owner wants. C'mon, PC makers, pick this up!
[via Engadget]