Because web design is a horrible abomination suffered by an enthusiastic few and a miserable many; because there is a fundamental, unsolved problem of presentin

Because web design is a horrible abomination suffered by an enthusiastic few and a miserable many; because there is a fundamental, unsolved problem of presenting a specific amount of information (not too much, not too little) to users in a medium which can be radically different from user to user. A design that would look good on your layout would look terrible on another user's widescreen; a design that would look good on a widescreen will look awkward, at best, on your setup. It doesn't help that so many people are still clinging to CSS as the primary answer for this, since it is completely ill-equipped to deal with this problem.