Earlier quoted context omitted.
Is it though? Backends can be any language and there's a lot more variety there -- TS+node, Go, Python, Java. It's just .NET that's largely ignored for no real technical basis.
You can easily use the same types and libraries in your backend and frontend with TypeScript. It’s not at easy with dotnet.
You can do that in .NET, too if you use Blazor for frontend.