Older format had 14 teams with two groups of seven with top four going in the quater final from each group. Group stages didn't had much excitement because there were two useless games. It was like having Germany,Brazil, Spain and Luxembourg in a group and top three going through.
So they cut down to 10 teams, with all teams playing each other like in a league and top four going in the semis. Good entertainment wise but harsh on smaller teams that won't get much chance on world stage.