[hiccuphippo]

It is still in active development and before v1. They haven't decided to make it unstable on purpose it's simply not done yet.

Anyone using it right now implicitly accepts that they'll have to keep track of the changes in the language and update their code accordingly.

[pezgrande]

The language is almost 10 years old and they are not planning a v1.0 anytime soon afaik.

[loeg]

Depending on how you look at it, Rust went like 9 years from inception to v1 (2006-2015). C went ~17 years before initial standardization (1972-1989).