Not sure this is the direction the OP intended, but its not like this "loyalty" issue is a recent trend in professional sports or League though, its been happening since the late 60's at least.
What is loyalty anyway, if a player who has been at a club for 10 years gets an downgraded contract, that he feels is insulting and decides to go elsewhere for more cash is that "disloyal"?
What about sports with drafts? AFL, NBA, NFL etc. your loyalty is up for grabs, you play all your juniors in a certain area, club system etc. and then suddenly your a moved 1000km away to play for a team.
I wonder do fans get upset in those sports? "Oh we went to the trouble of drafting him, now he is leaving"???
As a big nba fan i can say they definately do, though not to the scale that we do in the nrl. Small market teams are always losing stars that they have drafted after about three or four years. Its just the ways it is, stars wanna play in big market teams or contenders and big market teams want big stars, the fans of the small teams go through this regularly.
Cleveland couldnt even keep their hometown star who was handed the keys straight out of highschool.