I guess it does help by making the cost of adoption lower.

But my main point is that being an early adopter of a non-mainstream tech is fundamentally unpragmatic and usually people are driven to try something new by desire to try something __cool__ not by pragmatic considerations.

Well that usually has significant downsides too so it's not as simple as "do that". But yeah if you can do that it's a big benefit.

That is one thing that could be a killer feature and I like Zig for it, but I can see myself using a language without that level of interoperability if it has a good enough killer feature set

The success of TypeScript, a syntactic superset of JS and recently the fastest growing programming language, seems to confirm it.