If you think of the people that would naturally look to C# there are a lot of reasons why you might have an existing C++ codebase and migrate to a C#/C++ codebase. It's relatively straightforward to link the two languages where doing the same for Java is a lot more work. There are lots of legacy applications with decades-old business logic that can be glued into C# WinForms and work swimmingly. Java has this but the interop code is a lot of work.

Java applications also in my opinion struggle to feel 'native' especially on Windows to the same level of niceness as C#/C++.