There is a huge number of users that are still learning basics, very low experience. So their problems are usually ordinary problems. Upvoting this kind of question is the same as "I'm suffering this problem too". You know, many people uses "likes", the equivalent to upvoting. In my opinion it's a emotional response, humans are social beings.
A quick search in SO may offer short answers, easy to read and understand. The user likes it and upvote.
Hard subjects likely belong to more experienced users, whose amount is much more less than unexperienced users. So, if a difficult question has many upvotes it's due to a very good matter, well wordered, and very few results in a search. Same for answers.