Is this different from any other field of business or education?
In my experience, it's not. Workers seems to fall into a few select categories, the majority being those who apply themselves well, work hard and don't involve themselves in a lot of idle chatter-about 70% of the crew.
The next group is those who work well, enjoy the social nature of the workplace, and manage to keep the workplace a lively, enjoyable place-about 20%.
Then there are those who talk, talk, talk, let everyone know how great a job they do, but only really deliver about 20% of the time-about 7%.
Then the last group are those I affectionately ;) call "deadwood". They originally talked a good game, but when the rubber meets the road, they try their best to do the least and seem to just squeak by-thankfully, only about 3%. I include the perpetual whiners in this group.
Unfortunately, for whatever reason (usually poor management and recruiting), some workplaces seem to be heavily weighted with the great talkers and deadwood which ultimately discourages and drives away those willing to make a quality contribution to the operation.
It's too bad that most hiring is done just to put warm bodies in vacant positions without much attention given to screening out those who put a drag on the most effective people.