The careers are getting longer since they are starting earlier in age, theres now 8u-9u playing, where they used to start around 12. Your belief of 4-5 yrs would bring them to my next point, I'd say 15-16 yrs old is when they drop off , this weeds out the not so serious players and also thats when boys usually come into play.
Assuming they start in T-ball around 6 years of age I agree with HITTER23 that 15 years old or sophomore year of high school seems to weed a lot of girls from the sport. The reasoning is somewhat the same as HITTER23 as I put a little more salt into school ball playing a part in girls making some choices. Here's my opinion:
It appears to me that girls, for the most part, put more emphasis in being able to play-------not simply be a part of a team. Compared to boys, they appear to have less patience and have higher expectations. Boys seem to be able to accept that other boys have more natural talent without it affecting their attitude or perspective. Boys can be satisfied with simply having a uniform or a team jacket to wear. Girls want more and in many cases don't feel fulfilled, even if it is a supporting roll beneficial to the team performance.
Example: boys would remain on their baseball team if all they contributed was being a pinch runner at times. Most girls are not going to accept being an expert base-runner and professional slider as her job on a team. As a coach, we would welcome a race horse like this with open arms but a young lady wouldn't view this in such high regard.
I believe girls will give it till their sophomore age in the game and if they don't see much light at the immediate end to the tunnel they will look elsewhere to spend their time.
While times have improved, this has been evident in college for years as we watched team rosters favor younger players as the staple. The game was growing by leaps and bounds and the talent pool favored younger ladies that were getting a higher quality of coaching and game experience at a younger age. Freshman were coming in with more knowledge, honed talent, and competitive game experience than any of the juniors and seniors on the team. Coaches were quick to utilize this fresh talent and would sit juniors and seniors. The older girls felt betrayed because they thought there should be some loyalty from the coaching staff. Coaches were quick to point out if they wanted to play they needed to step their game up. Unfortunately, for many juniors and seniors they simply were born too soon and didn't get the same opportunities.
At this pivotal point in many of the girls' lives they would opt to graduate on time and favor class schedules over playing a game, leaving to pursue their education and go on with their adult lives. That's why the average age of rosters were so young. It was an easy out for older girls and an acceptable excuse. For many it left them empty, longing for the what it could have been, and left them emotionally damaged. To be honest, it would have been prudent for staff to provided counseling to the young ladies so they could put closure to their decision but few schools ever thought of it. Instead they remained focused to the "in the moment" team and winning.
Bad choice.........
This same thing occurs when the girls try out for jr. high and high school teams. Parents should really be aware of the emotional strain it puts on their daughters. The girls need comfort and support, especially if you are one of those parents that have put a lot of energy into being a part of the game. The girls don't want to let you down, even if they are ready to move on with their life. If you are one of those parents, you need to accept it and move on as well. Don't lose sight of the fact that the game is for them, not for your experience or void in your life.
I had an "old mentor" explain high school ball like this:
Freshmen want to make the team.
Sophomores want to start.
Juniors want to win it all.
Seniors want the awards.
It seems to have a ring of truth in many cases. Makes you think doesn't it..................