You can add a centimeter or so of thickness and get perfectly adequate cooling for high power parts - look at all the gaming laptops for an example of this (if you can get past the godawful visual design).

This isn't a "laptops" issue, this is an "ultra thin" issue. Trouble is most people only want to buy ultra thin laptops and don't realize that that super powerful 8 core cpu isn't any faster than a much less expensive one when there isn't adequate cooling.