Why bother making a thin laptop then? Why not have a chunky one? Surely it's all about economising the space whether it is on a desk or on your lap, the same priniciple applies.
Since this is the iMac forum I believe I correctly assumed the original poster was speaking of the iMac. Clearly the same principles do not apply to a PORTABLE machine. In the cas of a laptop, thinner and in effect lighter are much better, no question. Considering you will not be lugging your iMac around all over the place then it is not a big a deal.