C++ has been one of the best low-level coding languages for a long, long time. The compiled code runs efficiently and performance is hard to beat. Since it has been around longer than C#, C++ has been the core language for serious pro coders for a long time. With that said, what Epic is doing is catering to the upper echelon of serious programmers who probably have deeper skillsets and experience than do those who only code in C# or Javascript. That’s not to say that the latter two are bad, they’re fantastic languages, but C++ is the king of the pack. I’ve coded in all of them, and many others, and for serious game development, I’d do all my core game coding in C++.
Just my $.02.