Why structures are allocated in stack?

Thanks. Sorry for the delay in replying. But just trying to figure out why in C# they did it like this? In C++ paradigm structures and classes are treated as same(with some exceptions :-)). Is there any advantage by making structs are value types? and structs are sealed by default.

I think (not 100% sure) that structs are allocated in the stack because they are value types, 
meaning that you know exactly how much memory is needed for them. When you declare a class, 
in reality you just declare a reference (pointer) to an object in heap of that type (class), 
and you do not know before compiling, how much memory u will need. (keep in mind that a reference to a base class 
can easily point to one of the derived classes -typical late binding). 

Hope that helps