Do they actually contribute anything positive to society?
A large percentage of production in most industries has a negative impact on a societal level because market logic is independent of societal aspirations. Even in essential industries like the production of foodstuffs effort is largely wasted on nutritionally poor food we would be better off not producing from a societal level.
Are they so well paid only because of the hype?
My guess would be because they tend to live in high-cost metropolises, and have a bachelors degree. Their average pay is not dramatically different from the average bachelors degree holder.
What do programmers even do? Other than browsing reddit all day long.
Typically programming, meetings, etc. if I had to guess.