True, you can apply it to desktops, but those are bulkier and more expensive to ship. I've kept the box my laptop was shipped to me in, and it's got all bases covered if I need to send it back.

I'd wager that sending a laptop back and forth twice is probably about as expensive as a single round trip for a desktop, and with less risk of breakage, since all the parts are soldered in place, with much less wiggle room for heavier stuff to break off.