Same goes for many other things, such as cars, phones, and, yes, even laptops and such. The design has to appeal to me. Things that are overly complicated get on my nerves. This is perhaps one reason why I use a lot of products from Apple. Apple's sense of design is second to none (when it comes to high-tech, anyway. Porsche still makes the best-looking cars on the road, if you ask me).
Anyway, the simplicity of Google's sites and user interface is part of the reason I use them. For me, they just work. They are quick to figure out and don't clutter my screen with unnecessary buttons, graphics, links and such.
Turns out, this is all by design (pun intended). The Official Google Blog tells us how it goes about coming up with designs for its sites, and I find the insight interesting. Last year, Google's User Experience group set out to define what makes Google designs "Googley". The team came up with 10 design principles that form the basis of Google's design philosophy.