The height adjustment basically doesn’t matter, it’s such a small amount. I’m not going to argue that quill stems should never be used, but the design has many idiosyncrasies that has led to it mostly being phased out of all bikes except style bikes. They do have a classy and unique aesthetic that is more attractive than the blunt and utilitarian look of the threadless stem and will always be a part of bicycle culture. Just how they work makes them heavier and weaker than threadless stems in general, there is some overlap but by and large it is impossible for a quill to compete in those regards. The huge steel bolt and wedge is a factor but even if they could be made of aluminum (these designs do exist) the stem is still being held only by a small surface area with a lot of force, which makes them prone to slipping. The high force required to hold the stem can easily dent or notch the steerer tube, as has happened on most of my quill bikes, making fine adjustment much harder and ruling out aluminum or carbon fiber steerer tubes. The strength of the design is highly limited by the narrow diameter required to fit inside the steerer, even on 1 1/8″ quills, as well as having a long unsupported area. The quill is basically unsupported except by a single large wedge at the bottom, meaning the rare instance of the bolt or threads being damaged writes off the quill and anything attached to it completely. It’s not uncommon to have them secured with an eposed hex head bolt, which provides a large risk for a more serious injury in the event of a spill. Thankfully allen bolts are becoming more common but they can’t always be retrofitted to all quills. Also this is a specialty bolt that has to be basically the exact size and you’ll never find it anywhere outside the bicycle industry. It’s also quite common for them to not have detachable faceplates so a stem or bar swap necessitates fully uninstalling at least half of whatever is on the bars and then posing a high risk of scraping bars on the way out, which is a major problem for carbon. Plus from a mechanical perspective, the inner steerer tube diameter is a chokepoint which kinda makes things like a thicker bar clamp less useful for improving strength and stiffness, making bar clamps bigger than the existing 26mm kinda pointless. This means the average quill stem bike is going to have dramatically more “compliance” in the handlebars, which isn’t necessarily a bad thing for comfort but is a significant problem for performance riding. The sliding wedge design basically rules out carbon as a stem material though I suppose it could just be mostly carbon with an aluminum sliding face or something. Corrosion and getting really stuck is a severe problem with the design, and the only solution is to compromise the already low friction interface with the fork by adding grease or oil to repel water.

That’s just the problems with the stem, the system compromises fork design and complicates headset setup and maintenance to an unnecessary degree. While it is totally possible to design a threadless fork styled in the manner of a threaded one, nobody has bothered because the system is so limited and finnicky. Cutting threads in a fork weakens it, as well as ruling out usage with a different sized headtube. This was a severe problem “back in the day” because shops would need to stock or order a staggering array of forks to meet even a limited number of bike categories. Threadless forks can easily be cut and prepared by any mechanic to fit any frame, massively simplifying inventory. In theory one could do it on a dual-crown fork (but as far as I’m aware, nobody has been that daft) or use a steerer tube clamp, like a cantilever brace, on a threadless fork to skirt this issue, but you now need to find some means of preloading the headset sufficiently which would require another device and nobody has bothered as far as I’m aware. Needing to unthread two rings to service the headset slows service considerably, and the preload is notoriously difficult to dial both of which were factors leading to it being abolished first and heavily touted by race mechanics. I think quills are a great example of empirical design – bikes have been around waaaay longer than good machining tools and most systemic design methods, so people did what they could with what was available. The design is a mix of cheap and simple to produce, serviceable, and does what it needs to. There were much different expectations about what made a good bike and nobody wanted to upend the entire market for something that felt like a marginal difference. Kinda in the same vein as the problem with freewheels – rather than designing a new and better hub to handle more gears, people just kept stacking them and making the axle longer until it was readily apparent the design was limited.

A great read about this topic can be found [here](https://cyclingtips.com/2017/08/origins-how-the-aheadset-threadless-headset-changed-bikes-forever/) which explains some interesting bits of cycling history that covers how the Aheadset, Dia-Compe, Salsa, and RockShox to name a few swept the industry.