Why is MLB roster expansion still happening?

Every year it seems like people around baseball have the same discussion in September: why does the MLB still have roster expansion? It’s a fair question, given that September is make-or-break for most teams in the playoff hunt. So why does baseball still allow teams to expand their rosters?

For the first five months of the regular season, teams are allowed to have a 25-man roster on a given night. Teams will generally carry 12 or 13 pitchers, which makes bullpen management very important over the course of the season. The dynamics of managing the bench each night can also be a challenge, especially in the National League. Those challenges are all but eliminated in September, when teams can…