Why put a go-kart engine in a Camaro?

I was browsing some projects on Sourceforge yesterday and I came across a basic game of Checkers. I believe they were using GTK and maybe SDL as well. All of the source files were C++. Now, SDL works natively in C++, but as far as I know, you'd need to use GTKMM in order to write GTK code in C++. Nevertheless...

This person usesd absolutely NO features of C++ in his code. It was all straight-C. I really don't understand this at all. Why incur the extra overhead of the standard C++ libraries and then not use them? Secondly, why use C if you don't need to? When I say that, I'm referring to the need to do a lot of low-level memory manipulation, in-line assembly, and other things of the like. Of course, any of that stuff can be done in C++, but usually C is preferred. This application had none of that in it. It was just a bunch of structs, char*'s, and SDL/GTK library calls.

My stance on this particular instance is to just use C++ instead of simply changing the file extension to ".c". std::string is a lifesaver, and the C-style structs just get clumsy and very limited after a while, especially in a game. Those 2 things alone would have made the game more extensible, easier to maintain, and a lot easier to understand.

Just my two cents.