The threadless total setup including the stem is lighter and stiffer than a threaded quill, plus is easier to adjust length and bar height. So that's why they're used.

As far as why so many bad looking setups? To me, people being sold a wrong size bike, because everyone needs to buy the frame size they would have if they were a racer But it may also be that many frames only come in a few sizes, so you have to make it fit somehow.