Because why take time to learn things? As long as you can function properly I say your okay, sure you can learn things and farther develop yourself, or maybe you just want to stay at the bare bones essential and put your time towards other efforts. Maybe your lazy, you can function you have the bare bones why bother expanding on them, when they most likely won't impact your lifestyle drastically. At least that's my view point on it, you have the essentials, if you want to expand then good for you, if you don't, then good for you as well. Some people just put value in other things. Now on the other hand if it's so horrid that he has trouble functioning in society, that's when you should be worried.