Why companies advertise for jobs while the selection never count on applicant qualification but in pre designed selection (employment). ?

As per SOP and Rules of Service every post (Vacancy) needs to be advertised. so the hiring process remains neutral. 

For any company to  remain on top of the game has to acquire the talent and retain it. I believe no one would like to lose the game in any given field. 

The question poses some misunderstanding somehow. because every company must be hiring the best personals for its growth and need.