They may have beauty on their side but not breeding.
Quill stems are hugely problematic because of a design flaw. They generally attach to the fork's steerer by sliding inside it and then engaging an expander at the bottom of the stem. This leaves the top unsupported and allowed to move around inside the steerer. This causes three problems: 1) It causes circular fretting damage to the quill where it enters the headset. It is a problem for powerful riders because it leaves a massive stress riser where the quill can break. 2) The dynamic joint pumps water and sweat into the steerer, which then emulsifies with grease people (needlessly) put in there and causes corrosion of the aluminium to the point where the stem cannot be removed for servicing the headset. It than has to be sawn off and laboriously sawn down the length of the quill until the pressure is released and the stump can come out. 3) Bolt redundancy. There is only one bolt in there and if that fails, depending on the clamp's design, you have problems.
Both these are serious design flaws. The other problem is with removing and refitting handlebars. Unless it has some sort of front-loader arrangement or a hinge, fitting a handlebar through a quill stem's eye is like chasing a camel through a needle eye.
The aheadset threadless stem sorted out al these problems plus added many other advantages we didn't even think of until Mr Aheadset came onto the scene with his ingenious design some 27 years ago.
