I assume in Predator 2 the elder just considered that since the human had gained City-Hunter`s honour when he killed him, he disurved a trophy.
And in AvP maybe the elder wanted to emply that he recognises the human species` merits in this age and that there is no point considering them simply prey or hosts for xenomorphs, but equals, or at least tolerated as a superior species, no longer just big game. This could also be linked to why no predator was interested in a huge ship blowing up in Alien, and why no cleaner was sent (yes, i know the concept of AvP wasn`t something as popular then as it is now, but if AvP and Alien are ever supposed to be linked, then what the hell), as that is a time when Predators no longer hunt humans, nor do they interfere with their affairs.
Yea, i know, i don`t like it either, but it just came to me on the spot.