I was thinking more of the kid who was struggling in pre K or in their earlier years because of speech or developmental delays or is just plain immature. Parent decides at a young age that they would do better with another year of development.
Having an extra year before going to college isn't bad either not everyone is a great student or has their act together right after hs.
I try not to be too judgemental of this as my son struggled in his earlier years with school but is now an honor roll student.
I probably would not hold back exclusively for sports but I look at some of my sons friends at 14 and being a late bloomer can be really tough.