why can't we create our own ostream object

If cout is an object of ostream class, then why can't we declare our own object, say, 'out' from the same class. i.e, isn't the following code supposed to work??

#include<iostream>
using namespace std;
int main()
{
    ostream out;
    out<<"something";
}

or otherwise

#include<iostream>
using namespace std;
int main()
{
    ostream_withassign out;
    out<<"something";
}