For Jr JPBO, it's to mirror the real [LEAGUE REDACTED] farm system that up until two years ago had subleagues of 5 and 7 teams.
Here it's because there's such a HUGE gap between the Eastern and Western teams, and a lot of larger cities are in that Quebec-to-Windsor corridor.
It also means
the schedule for the league will focus on divisional play to minimize travel requirements. Also thinking division leaders plus one wild card from the East make the playoffs.