I'm not really sure that the 'elite' track has a lot to do with that drop out figure, if you think about how many girls take up (and drop out of) gymnastics, as against the small number on the 'elite' path. Even in our gym, which has a strong elite program, they are only around 5%ish of the total number of girls in the club. Not enough to majorly influence those figures.
I also think I remember reading a piece recently about the most common age for girls to drop off the elite path being 12. It sounds about right to me - its the age when ability will be tested by hormones, growth spurts and other distractions. Or even where, despite best efforts, they plateau out and can't quite take the next step up.
At the lower levels, in my experience (which I accept is limited) the numbers seem to be quite static. I haven't seen a big drop out at level 3. Level 5, yes. And then older. In between, the girls are just starting to understand what the rewards might be. They see girls they know, or have competed against, making starter squad or being opportunities to travel and it's pretty motivating. Some club shuffling sees to go on but, in our club at least, relatively few girls drop off the elite path between level 5 and espoir, unless they are injured. And several of those who do move across to national grades because they still can. The numbers are quite small in context.
I suspect the biggest number of girls giving up at 10 are the others. The ones who are working hard and doing well but, because of the way the system is set up, they get to realising that maybe future options are narrowing and/or they have reached a skill level which possibly requires more hours to increase much more. And the rec girls who come and go, once they've gained a few skills. Making those girls feel more valued and giving them greater incentive to keep going will be key to upping that drop out age in my opinion.