I've heard my complaint be called an excuse before, but consider that it's also the first barrier. Not a big one when you already decided to take a course, when you're seriously interested, when you just look them up and soon enough you know the conventions in the field. That's different from casual reading on HN, though. And tell me, are scientists not a class that is looked up to where you live? The common Joe might not explicitly say so, but if someone is a "scientist" then you don't expect them to be stupid or muck out stalls; they do have some real status. This doesn't come from doing things that seem like any common Joe can do it, yet a lot of the work is just that. Once you start paying attention to how often "new research" in the news amounted to a big survey and very basic statistics, or playing around with a Kinect in a train station to learn about walking patterns, it doesn't seem so different from what regular HN readers do for a living. If you take the paper behind such a survey, it'll turn out to be full of complexity that is a lot harder to get through than necessary. It could be a lot more accessible, but then they would lose status.

It seems to me that brevity is the real excuse here. Moreover, if it were just about symbols but papers were otherwise accessibly written (to reasonable extents, obviously), that would be different still. This is not the case.

Appearances are probably also important for funding. I'd bet that if you submitted same proposal twice, once phrased in a convoluted way and once phrased in a "we're gonna blow up some material multiple times and see how far the shards fly" style, a number of times to independent funding committees, there would be a statistically significant correlation with which proposal gets funded.