Fetching a simple cup often acts as a mysteriously humanising force for celebrities - "a common denominator," as Rea put it - because it's affordable and often part of a daily ritual.
Coffee used to do the opposite, acting as visual evidence that celebrities were way cooler than the rest of us.
Coffee has "always been a part of the fabric of the Hollywood scene" because of early morning call times, according to Rea. His 192-page book, published in 2015, is filled with vintage photographs that feature actors drinking coffee on and off set. There are shots of Lauren Bacall and Humphrey Bogart making it at home with fancy gadgets, and others of Grace Kelly and Steve McQueen at the craft services table on movie sets.
"It became a Hollywood habit, mostly in good ways," he said.
"If you're going to have an addiction, coffee is one where the downsides aren't that bad."
A steaming mug at a cafe offered what Rea called the "European sophistication factor".
Hollywood has had ties to Europe from the silent era onward, when actors and film-makers came from the continent's major cities and brought their coffee habits with them.
Some Americans contributed to the development of this trend, too, adopting habits from their time abroad in the early 20th century. F. Scott Fitzgerald and Ernest Hemingway, for instance, spent time in Europe during their formative years, Rea said.Both returned to the United States and worked in Hollywood, bringing back aspects of the coffee culture of Paris' literary and art circles.
But no longer. Purchasing brewed coffee became ubiquitous with the rise of second-wave coffee culture in the 1990s, according to Sarah Lyon, an associate professor of anthropology at the University of Kentucky.
Going to Starbucks is a "middle-class luxury," something that many people can afford on a semi-regular basis.
"I think it's a way for middle America to identify with the stars, through a small luxury, but not in this elitist way," Lyon said. "If he was going to some sort of elitist, third-wave coffee shop where they were having their $5 pour-over coffee, people wouldn't identify ... the same way."
Lyon specified that it's the act of grabbing the drink themselves that humanises the celebrities, who could easily staff it out.
Jerry Seinfeld's Emmy-nominated web series Comedians in Cars Getting Coffee plays off this idea by having Seinfeld drive his guest across town to get a cup.
When asked by NPR why he chose coffee, Seinfeld replied: "That whole description of why it's great to meet someone for a cup of coffee - the ease, the simplicity, the compactness. And that it also obviously gets people talking."
