Funny you use Rolex vs Timex as an example. I'm into mechanical watches. There are many, MANY watches that make Rolex look cheap, that are MUCH lighter (and thinner).
A Patek Phillipe for example. A much higher end watch, which is also far lighter and thinner than any Rolex. Audemars Piguet is another higher end watch co. that uses forged carbon for some of their cases. Those watches which cost 10 times what a typical Rolex does, are extremely light, and that's kind of the point. In certain areas, where lighter is seen as desirable, and smart phones is one such area, lighter is a good thing, and, one that's costs money to produce, all else being equal. I foresee most smartphones getting lighter and lighter as technology allows while retaining the same strength and functionality. Apple is ahead of the curve on this IMO.
I would think that if you asked someone, assuming the quality, power, functionality is the same, would you rather have a heavier smartphone, laptop, etc. or a lighter one, most would say, we'll if its the same (or better) quality as the heavier one, ill take the light one. Why wouldn't you?

If weight doesn't equal quality, why would you prefer heavy to light?