Disparity in prospect rankings

There has always been some differences among the recruiting publications (espn, on3, rivals, 247), but this year it appears more extreme. On3 has each player and their ranking on all recruiting sites. This year it seems more disparity (not always). A good example is recent commitment Jelani Watkins (55,22,10,64). Do each have the same hs tapes? does ranking have to do with attendance at recruiting site camps? Or, horribly, is it politics?