User blog comment:Nerdybeast/Patch Notes/@comment-4080931-20120123073426

Since Riot is catering to a more casual crowd, they have skills and mechanics that make you go "oh, so that's what he does" or "death recap... Ashe shoots that big icy arrow?". The game is made so that the main playerbase doesn't really need to look up this sort of stuff. However, this means that some of the playerbase isn't used to or doesn't bother looking up patch notes either, as shown from your experience.

If they were catering to HoN and DotA players, then you can expect players that are dedicated enough to look up Patch notes.