That's basically an artifact of the combination of Rust's immaturity and its conservative stability policy - once a language feature or API is supported by a stable compiler, it needs to keep working more or less forever. So a bunch of features still require nightly, so some projects target nightly, and the big ones may pin to specific nightlies. But the amount of breakage is vastly lower than it used to be (especially pre-1.0), and even in the year-and-a-half since 1.0 a lot of different bits have been stabilized, so that sticking to stable Rust no longer feels like being handcuffed. The biggest unstable feature left is compiler plugins, which should get a rudimentary version stabilized Real Soon Now. With that and maybe specialization in place, there should be little reason for projects to stick to nightly.