Yes, it probably is easier to forge square than round. At least it is quicker. 
 
However, I would put it to you that form follows function. 
 
The job is identified, and the tool is produced to do the job. 
 
If we want a handle to turn easily, we provide a round tang. 
 
If we do not want a handle to turn, we provide a tang with sides.
		 
		
		
		
		
		
		
		
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