If you're developing, you generally have control over the development environment (+/-) and you can install things. Plus that already reduces the audience: set of people with oddball hardware (as someone here put it) intersected with the set of people with locked down development environments.

Let alone the fact that conceptually people with locked down environments are precisely those would really want the extra safety offered by Rust.

I know that real life is messy but if we don't keep pressing, nothing improves.