I think it's not about that but about dogfooding Swift on the server. Apple uses Go, Java etc for a lot of its server components and refused to invest in hiring people that would extend the ecosystem for server Swift.

Thats the problem.

It certainly doesn't help, but among big tech, Apple is not the only company where teams are siloed and independent. Microsoft has people writing Java or Go instead of C# too.

I assume the server side usage is not zero, but not enough to reach a critical mass, you're probably right there.