Mozilla was heavily involved in the early development of Rust (and since there is no Rust Foundation, is the holder of the Rust trademarks etc.).
But at this point however you can't really call it a Mozilla project as active development is no longer dominated by Mozilla employees. Holding the trademark is just a formality owing to there not being a better way to do that without starting up a new Foundation.
The answer might turn out to be that it makes bicyclists less safe.
A couple of years ago I moved to a place with extensive bike lanes and other bike-friendly signage, road features, etc. Sounds awesome. But I've noticed that it significantly adds to the mental load of driving here. I'm an unusually conscientious driver, and I often encounter the feeling of hitting my multitasking ceiling at intersections, partly due to the bicycle-friendly increase in complexity. I suspect that many less careful blow through that ceiling without realizing it.
I think this is a real phenomena. Many traffic engineers don't seem to appreciate it.
Earlier this year I did a small study of how often drivers yield to me, a cylist, at certain crossings. These crossings are rather confusing, but the city seems to believe that merely putting signs (sometimes multiple in basically the same spot) telling drivers to yield to cyclists is enough. It's not. Drivers nearly run over cyclists on a regular basis at these crossings. According to my statistics drivers yield to cyclists only about 61% of the time. See the slides here:
That's a great example of an over-complex pattern. The yield sign is awful--hard to even tell whether it's for the cars or the bicycles.
Here's what worked for me, over thousands of miles of cycling back before bike lanes, etc.:
1. I rode as far right as I safely could, typically on the white line or a foot away from the curb, and always with the flow of traffic.
2. I was careful to ride in a straight line, following a completely predictable path.
3. I had a glasses-mounted rear-view mirror and kept an eye on traffic coming up behind. I never needed to, but I was always ready to bail out to the right in a split second. Towards that end, kept my bike in top shape and practiced quick stops and counter-steering.
4. Never made left turns if vehicles were present. Instead, passed through the intersection, stopped on far side, dismounted, and lifted/turned bike 90 degrees.
5. Reflective gear day and night. Never rode in poor visibility (e.g., rain storm).
6. Most importantly, always yielded to all vehicular traffic all of the time. If a car could intersect my path, I just stopped and waited, unless I could make eye contact and it was clear that they saw me and intended to wait.
With that, never had a close call, nor even got honked at.
Now, you might say that that's not fair, or that you don't want to ride in such a wimpy style. I understand. But I think it's the only safe(-ish) way to ride on public streets.
I come in on the weekends sometimes, because I'm bored or lonely or have work that needs to be done. I get paid for the privilege and I love my job, and it means I never have to stay past 5 during the week. Granted I work in academia where the norm is to stay till 8:00 and weekend work is necessitated by the projects we work on, but I personally don't have to. If I had a family things would be different though.
Using nightly features is as simple as inserting +nightly as the first argument to rustc or cargo (assuming rust was installed with rustup, which is the default way to install it).
So in this case, it's just `rustc +nightly green_threads.rs`
If the point is to explain how green threads work, it is better to use a common language so people can simply try to understand the concept and not try to understand both the concept and the language at the same time.
