Agreed, however if you switch to a team where the ones sitting are now in the top 9, it is obviously a weaker team, and someone will still be the worst players on the team and someone will still be sitting and watching. 4-5 girls sitting is still too many.
It's either a weaker team, or a team that has a need at a particular position. Especially at the younger ages, playing time and quality of coaching is more important than how many games the team wins.
For tournaments, I like 13. With DP/Flex, that's 10. CRs for P and C makes 12. Plus 1 in reserve for injury.