People assume everything is well motivated
I repeatedly get reports and issues filed from people who have questions about stuff in the code or about certain behavior. They assume that since it is done in a special way in the code it is done so by careful research and precise coding resulted in those choices and thus they do not complain or ask about it to us and instead write angry blog posts somewhere else.
The truth is that development is to a large degree evolutionary and unless someone reports a problem with a particular solution, it often sticks the way it was done when it was first made to work. Even though it might not be perfect and perhaps over time turns out to be a rather half-baked way. Many are also the fixes that are "temporary" and then just never get around to get modified or fixed. And why change something that works?
Not to mention that most projects also have a list of things they would like to change or fix one day but that nobody ever gets around to actually doing.