APs can help with general education or advance standing. Or make you feel good if you have nothing better to do 
AP Psychology and AP Human Geography are on the easy side ā the reason why percentages are lower is because you have freshmen taking human geography and more of the average student taking psychology as it is known as one of the easier APs. I know a good number of people that have self-studied these APs and got a 5 ā and it helps to be generally knowledged about the world / an upperclassman with experience from other social sciences and extracurriculars to already know most of the material for some of the APs self-studied. Someone I know took 1-2 days going through a review book and got a 5 on human geography without the course.