This is an interesting topic. At the last place I coached at before I got out of the biz to actually make some sensible money to support my family, I was the cross country coach and track coach in charge of distances.
When I started there, I had a limit of 8-9 distance runners that would carry over and have a "safe spot" waiting for them on the track roster. Any runners over that number, i.e. the 10-lets say through 18 spots, would be told that they could have a training outline for indoor & outdoor track, and that they could run in home meets unattached. They would also be allowed to try out for cross team the next year.
The reason that we did this was that we had a roster limit for males imposed by the AD for the TRACK team. We did not have a roster limit for the women, and in fact were encouraged to get to 100 females if possible. When you factor in sprints, jumps, throwers, multis, and distance, and if every coach gets a similar number of athletes, then you limit out at about 50 male athletes.
Over my time there we were allowed to stretch the track roster to 60 and I was able to scrap & scrape up to 14 full time year round distance runners, which at a mid-major, all things considered, was a manageable number considering I was also the women's coach and I had no assistant or G.A.
So to answer your question, my own distance team had limits imposed by my head coach, who had limits imposed by the AD, who had overall limits imposed by our Title IX number that we had to hit, i.e. proportion of male to female participation with regard to our student body ratio. Hope that helps.