Good question! I have always wondered why a company might ask the court for a winding up order by passing a special resolution when, by passing a special resolution, they could put the company into voluntary liquidation!
I think the answer possibly lies in the principle that, by getting the court involved, it means the court will ( admittedly, indirectly ) be supervising the process. Otherwise, who can tell the wierd and wonderful rationale behind this course of action?