Growing in absolute numbers doesn't mean growing the market share, and even a growing market share is not necessarily sufficiently fast growth to become a safe bet. All languages that ended up becoming very popular grew their market share much faster than Rust does. Being an old language with some real market share is obviously better than being an old language with negligible market share, but being an old language with real, but small, market share is not exactly a sign of confidence.
It's true that the total market share for low level languages (C + C++ + Rust + Zig + others) continues declining, as it has for a couple of decades now (that may change if coding agents start writing everything in C [1] but it's not happening yet), but that's all the more reason to find some "safe bet" within that diminishing total market. Rust's modest success is enough for some, but clearly not enough for many others to be seen as a safe bet.
Do you know of a good way to measure market share? I know of GitHub's and StackOverflow's surveys, but I'm not sure how well they reflect reality. There is also Redmonk.
GitHub's survey did not say much about Rust I think, despite Rust projects often having lots of starring. Rust projects might have a greater ratio of stars-to-popularity than projects in other languages, though.
StackOverflow's survey was much more optimistic or indicated popularity for Rust.
Redmonk places Rust at place 19th.
The best sources are industry studies by market research companies that collect information from companies. The best public sources, IMO, are those based on job openings (as jobs correlate more with total number of lines of code than sources based on number of repos, PRs, or questions). Some of these are about a year out-of-date:
https://www.devjobsscanner.com/blog/top-8-most-demanded-prog...
https://uk.indeed.com/career-advice/career-development/codin...
https://www.itransition.com/developers/in-demand-programming...
https://www.hackerrank.com/blog/top-developer-skills-in-2025...
Viewing these numbers through an optimistic or pessimistic lens is a matter of perspective and, of course, no one knows the future. But when you compare Rust, which is a middle-aged language now, to how languages that ended up "making it" were at the same age, the comparison is not favourable.
The first genuinely usable version of Rust was only released in late 2018. Rust is a very new language still.