Everyone forgets the ridiculous travel to get all 15 matches in over five weeks. China to Argentina at 38 hours of travel for the USA Women just stupid.
Even in the 9 match World GP days, some teams played two or three times against the same opponents.
The multiple pools of 8 allow fans to see many different teams in one venue over multiple days. It is good for the fans, plus with weeks off in between allows for travel, sightseeing and practice for the teams as well.