It strikes me as quite arbitrary, its isn't necessarily the end of the takeoff segments nor a threshold for ECAM actions, just a map dot, but offers the 'advantage' of allowing the aircraft to enter Nav mode right after takeoff. I just delete that waypoint at the earliest possible opportunity for our usual radar vector clearances. More evidence that individuals with actual knowledge of the airspace system entered the design equation long after the engineers had set the foundations. An erudite ppruner will be along shortly to correct me.