Why structs and classes instanciations are made differently ?

[Houdini via Digitalmars-d-learn]

Hello,

I am a C++ coder, and I am learning D (just reading a book, for 
now).

D is very similar to C++ (and also grabs godd ideas from Python), 
but I have a naive question : why does Walter Bright chose to 
instanciate classes like in Java ? And why is it different for 
structs ?