The original question was about whether there was a point to having to learn about ICAO and other 'obscure' topics.
I'm with frontlefthamster on this. As a PPL, you'll proibably only have to pass an exam on Air Law once and thereafter your licence will qualify you to fly throughout pretty much any part of the world. Many countries have their own local variations to international standards but in order to understand how these variations affect you it's important to know what the baseline is (or, at least, where to look it up). I guess the exam is an attempt to ensure that, maybe 20 years after you took the exam, you'll have a chance at finding some information that has suddenly become important.
Sadly it doesn't seem to work because it it quite clear from other threads, for example
the one which started on RT phraseology, that many people don't understand the basic ICAO rules and to appreciate what are local variations and thus are unable to pursue a reasoned discussion on the subject.