Relationships change over the course of a century. The 2% GDP defense spending agreement came about during the Riga summit in 2006. So the objective did change twenty years ago and many member nations never abided by that agreement; much to the frustration of both Bush and Obama. What you're espousing is more of a history rewrite by assuming we have had a static relationship going back to the end of WW2 and that this defense spending agreement is newer than it actually is.