A pilot friend of mine (the guy who got me started on all this) reckons that all this is in lieu of an actual intelligence test, which would no doubt be considered discriminatory. So instead you have to learn and remember zillions of largely useless bits and pieces. It's not THAT hard though it does sometimes seem kind of silly.
When I did my CPL the theory test was full of questions involving NDBs and wind drift - exercises in mental trigonometry, like you're going to be embarking on that when you're already distracted and disoriented flying in clag and turbulence. In the US at least, they were at the same time embarking on a program to decommission all the NDBs. (I think those questions have gone now). And guess how many on GPS...? You don't need me to tell you the answer.
My personal favourite is the three definitions of "night" and when they apply (in FAA land anyway).