Why C++, not C# coding?

#1 These engines are evolutionary steps forward from their earlier versions, and so use the same language. For C#, you'd have to rewrite the entire engine from the ground up- not that that would be a bad thing, but going through the engine versions from V12 to TGE to TGEA to T3D, that wasn't done.

#2 As Ted says, Torque has always been a framework developed in C++, since the times when it was the only language that allowed the kind of performance and ductility needed for game development.

Even today, it is arguably the best, performance wise.

TorqueX, on the other hand, was developed with the very specific purpose of having a game engine, over the XNA framework, and thats why it makes use of C#.

#3 You also have to take into account portability. C# is windows only.

edit:
Unless you use 3rd party open source projects like MONO or ROTOR, but these projects support only a subset of the .NET platform.

#4 Thanks to all of you for answers.