Can someone explain the benefits of using a Primary Interop Assembly in .Net?

object _comObject;
Type _comObjectType;
_comObjectType = Type.GetTypeFromProgID("MyCompany.MyApplication.MyObject", true);
_comObject = Activator.CreateInstance(_comObjectType);

string name = (string)_comObjectType.InvokeMember("GetCustomerName", BindingFlags.InvokeMethod, null, _comObject, , new object [] { _customerId });

MyCompany.MyApplication.MyObject obj = new MyObject();
string name = obj.GetCustomerName(_customerId);