singleton pattern really necessary?

singleton pattern really necessary?

[Shriramana Sharma]

I was wondering, if a person wants there to be only one instance of a 
class, they can simply do something like:

class {
<class definition here>
} classInstance ;

which automatically creates a single instance of a class. Why go to the 
extent of locking the constructor, copy constructor, operator= etc? The 
only possible thing (that I can think of) that cannot be done is 
conveniently passing it as an argument to a function. Is there any other 
reason that would make a class-name necessary?

Shriramana Sharma.