People think you're saying MRSA, and they tune out. I've seen it happening over and over now.
Actually listening to what other people are saying and trying to comprehend what they do and (and most importantly) don't mean just isn't a valued part of American culture.
When you were younger, did you ever work an entry-level customer service type of job? Then you know all about it. You see this behavior even in people who are actively seeking and truly do need your advice. I think it's a form of puerile impatience (that ends up costing more time ironically enough). It could also be an attempt to show a false superiority and independence, since it is most often seen in helpless people who are unable to perform even the most basic observation and problem-solving (think Freudian projection).