Your concerns about pitting two unevenly matched teams is legit. I just don't think that further dividing by age is the best solution. The current setup -- having age divisions two years apart, then dividing by skill depending on who shows up to a particular tournament -- works best, IMO.Well then by this logic why separate the groups at all? Why separate it in boys baseball? They have 8,9,10,11u, why bother splitting it all up then?why even have separate boys and girls teams?
Look at it from a tournament director's standpoint. If you have more age divisions, you're more likely to have an entry list that too often just doesn't work. You might have three 11U teams & nine 12U teams on an given weekend. Better to have a larger number - 12 teams overall in 12U - and then divide them in half based on skill.
I have no real experience with travel baseball, but more age divisions might work if you have more teams. Guessing here, but I imagine that there are more travel baseball teams than softball teams.
What you say about having any age divisions is not that ridiculous, actually. But the age divisions make it easier for teams to find appropriate competition. Plus, teams want to measure themselves against teams of similar age.