Is it compulsory?

Come the sunset of a sporting career, the publication of memoir and experiences into a fully fledged book is the requisite (or seems to be) for retiring from the sport “that gave you so 

much”

I ponder how much is this a way for these athletes to reflect, to give back to the public who are interested in them, or does it finally laud what is lost; their career?

I’d consider that it is a combination of all three.

Thoughts?