At least in my area I don’t think they’re under enrolled. STEM folks would obviously want to avoid them in most cases, but they do make for an easy A requirement if you just repeat the dogma and need a breadth requirement, and as majors they work well to get the diversity admits and people giving up on harder classes. They are religious in nature, so for them it’s like they get to not take hard classes and get to be closer to God, only in a perverse way. If it were all true or useful it would be compelling to learn in the same way a devout Christian might major in theology.