The only reason why this isn't apparent is because a vast majority of scissor switches are developed to be as compact as possible. The fact that the community is not pursuing a 4mm performance scissor switch is a travesty.
Scissors with up to 3.2 mm travel exist. Really nice, yes. (Logitech PerfectStroke)
But there are several of variables here, and a long way from idea to practice. Sliders are often stable
enough, well-known and robust.
Scissor legs tend to break easily, even on the somewhat thicker legs on the 3.2 mm switch.
The community here does not build switches on its own, at least not entirely new switches.
Many
ideas have been proposed, but the barriers for a hobbyist to start manufacturing something like that with high-precision are simply too high.
Some ideas for slider variants have been picked up by mainstream manufacturers and sold as custom. Some springs have been replaced. Some lubrication. That's it. That's what Zeal PC, Input.Club, Massdrop and Kbdfans have done.
Maybe switches with a combination of slider and a single stabiliser (scissors are
two stabilisers) would be the future. Some low-profile Kailh switches have them, as well as Bloody LK Libra (full size). Longer keys on Topre also have the stabiliser inside the switch, stabilising the single slider making swapping keys much easier.
I find it somewhat unfortunate, however, that Cherry MX mount has become so prolific. Nowadays, if a switch is to become popular it would need to be Cherry MX keycap-compatible.
Is there such a thing as a capacitive sensing scissor switch? That would be interesting.
The minimal
TextBlade was ... but not really. It used one physical scissor-key for three (or six) keys. In the bottom of each key assembly, there were three (or six) capacitive sensors that sensed the proximity of the user's finger-tip as it pressed down in one of three (or six) positions on the key surface.
The company was a disaster. I don't think they shipped any products. (Read the end of the thread)