Earlier quoted context omitted.
For a barber, more haircuts = more money. Trying to imagine what kind of relationship you think epidemiologists have with money? It's not like they get a nickel for every person they save from getting sick.
Not everything is purely about money. People are highly motivated by a sense of power or prominence, by a sense of belonging in the "correct group", and by a sense of being useful or productive at their profession. A barber as much as money will believe their haircut will make you look good.
PS: For people who wonder, the H factor-style ranking mechanisms for researchers means that your rank is higher (which tends to translate to more interesting work and/or more money) if you're heavily quoted by other researchers.
Of course, the easiest way to be heavily quoted, unless you're already a highly established scientist, is by being contrarian/provocative, so that other people feel like they need to debunk your writings.