whats the point in provisionals?

just wondering what the point in provisionals is. i was bronze 5 last season. played my provisionals for season 5 won 7 out of 10 and carried every game i won and still got placed back in bronze 5. if me doing well in my provisionals isnt going to help me climb or place me any higher why waste my time when i could just be starting to climb bronze from the start. why not just place me back in bronze 5 not do provisionals and let me climb. those 5 games were a complete waste of my time.