I think I haven't made myself clear..I'm not talking about just "top-flight" coaching, but earning a living in a coaching capacity, as distinct from a playing capacity (or indeed as a cab driver). Of course, few people can succeed for a long time at the top level; that's as true in SL as any other walk of life.
Someone who becomes a Rugby League coach on retiring as a player in their early thirties has potentially thirty more years of earning a living that way (not necessarily on £200k p.a., but paying the mortgage). A player doesn't have that option.