
A: There are many reasons not to use quill stems anymore: the industry as a whole has virtually abandoned this standard for the advantages of the threadless system so there are fewer varieties of quill stems available as well as headsets for said bikes. The popularity of threadless stems and headsets began about fifteen years ago when mountain-style bikes flourished and has continued on an upward trend since. The hold-out for the conversion was road bikes, which more or less as a whole managed to fend off the frenzy for threadless stems for about 6-8 years probably due to the traditional look of the road bicycle and because threadless stems were associated with "overbuilt" and "heavy" mountain bikes. But as the shore and streams return to the sea, the quill stem is a constant. They've been with us this whole time and shall remain. The fact that these parts are still being made (in two flavors: really cheap or overly nice) proves that as a system it's no failure. Though it's only an option, I still prefer to build frames for quill stems. Why?
* Esthetics. They simply look nicer, more "right," on a classically-styled steel frame.
* Tradition. This was the standard for decades. In "Stars and Water Carriers" you don't see Eddy Mercx fumbling around with spacers trying to set his stem at the exact right height. No, this classic scene of anal-retention features a quill stem.
* Because I can. The industry on a whole is slave to the whims and fancies of the masses and the whims and fancies of what the industry thinks it best for itself. Threadless stems make life easier for the Asian women and children that are assembling legions of bicycles destined for America. We're doing it for them. As a one-person, stalwart operation I can tell some one they're getting a quill stem and they'll reply "ok, cool."
* Lugs and Stuff. Due to the high-cost of casting I have more and better lug and fork crowns options available to me when quill stems are an option.
* Ease of adjustablity. One 6mm allen wrench is all you need to loosen the wedge and slide the stem up and down. No spacers, no adjusting the headset necessary. Stem too short? Nitto's Technomic stem has a towering 5" of adjustability. Tall threadless systems, especially involving the clamp-on steerer tube extenders, are an affront to God and Creation.
* Sheer Jackass-ery. I like doing things differently. It's fun to be a "manufacturer" and have the luxury of rebuffing the general trends and follies of the big-guys from a safe distance.
But let's face it. It's just a bike. Whether it's got one stem or another I don't really care. I'm doing my part and offering the quill stem option because it's a viable alternative and represents good design.