Thinner Gadgets - Do We Really Need Them?

It seems that every electric company out there is obsessed with shrinking the thickness of their gadgets. Apple showed us how thin iPad 2 is than the original iPad. Then Samsung showed us how Samsung Galaxy SII is the thinnest smartphone available in the market and it seems that everyone wants to out 'thinner' everything. I wonder whether engineers really prefer thinner gadgets? I mean, just give us a gadget that offers features - but at the same time offers better battery as well and a 1 cm thick gadget is more than enough technical achievement.

What do you think?