So how to explain someone like Sam Shepard, who was both a Pulitzer Prize-winning playwright and an Oscar-nominated actor -- not to mention a novelist and short story writer -- in an age unaccustomed to such masterly jack-of-all-tradesmanship?
Shepard, who died Thursday at 73, was the last person to explain such anomalies, because he seemed for much of his crowded, colorful life to be unfazed by what others thought. He appeared more willing to talk about ranching or breaking horses or other ruggedly mundane activities.
Such wide-open-spaces avocations seemed to belie Shepard's ascension in the insurgent Off- and Off-Off-Broadway theater scene of the 1960s. It was there that he began making his name as a stage actor and a writer of plays that were edgy, surrealistic and poetically allusive in the manner of the progressive rock-and-roll music of that era.
In those days, Shepard took some of the European-inspired absurdist humor and insinuating menace of such playwrights as Samuel Beckett, Eugene Ionesco and Harold Pinter and gave those motifs a distinctly American accent through such plays as "La Turista," "The Tooth of Crime" and "Geography of a Horse Dreamer."
Beginning in the late 1970s Shepard's plays acquired a depth, richness and profound sense of place, which put him within, or at least very near, the company of such honored American dramatists as Eugene O'Neill and Tennessee Williams. The idiosyncratic humor and eccentric characterizations of those early plays were still found in "Curse of the Starving Class" (1978), the Pulitzer-winning "Buried Child" (1978), "True West," (1980) "Fool for Love" (1983) and "A Lie of the Mind"(1985).
But Shepard's instinctive sense of dramatic form had by this time melded with a tragic, melancholy sense of all-American dreams somehow gone horribly wrong.
All of which would have been enough to seal Shepard's name indelibly in the nation's cultural firmament. But at about the time his playwriting was beginning to peak, he did something one would have never imagined O'Neill or Williams doing: He became a romantic movie lead.
The shift was so unexpected that many of his fans in the theater thought it had to be somebody else when his name appeared with Richard Gere's and Brooke Adams' among the leads in "Days of Heaven," Terrence Malick's 1978 saga of a romantic triangle in the early 20th century Texas panhandle. But his on-screen magnetism was powerful enough to match, if not overpower, Gere's own.
Critics and audiences alike compared his lean, laconic presence with Gary Cooper's. For a time, it was possible to believe this wordsmith would assume Cooper's legacy in the contemporary movie-star pantheon with the successive "Resurrection" (1980), "Raggedy Man" (1981), "Frances" (1982) -- whose star, Jessica Lange, became his longtime romantic partner -- and the movie for which he is still best remembered, "The Right Stuff" (1983).
Though Shepard didn't physically resemble Chuck Yeager, the real-life test pilot who most embodied the movie's eponymous "Right Stuff," the actor-playwright's sense of cool evoked the original's no-sweat bravado and prickly, let's-get-it-done resolve. He was rewarded with an Academy Award nomination for best supporting actor, which he lost (and this is somewhat ironic) to Jack Nicholson for playing an astronaut in "Terms of Endearment."
Shepard never had a movie role quite as celebrated after that. But he remained for much of his life a reliably compelling on-screen performer, mostly in supporting roles in such diverse films as "The Pelican Brief," "Black Hawk Down" and "The Assassination of Jesse James by the Coward Robert Ford."
One of his few starring roles on the big screen after the turn of the millennium was in 2005's "Don't Come Knocking." Directed by Wim Wenders, for whom Shepard wrote his finest screenplay, "Paris Texas" (1984), the movie followed the peripatetic, self-loathing movie cowboy Howard Spence as he rides away from a movie shoot to find solace in his past.
Though the movie wasn't as popular or well received as it should have been, one senses that Shepard invested more of his own reclusive self into this role than in any other.
Throughout, he continued to work with his other muse as both writer and teacher. And, by the way, he continued to ranch. That wasn't changing.
Speaking of changes, Shepard, at the start of his career went by the name Steve Rogers (his real full name was Samuel Shepard Rogers III). Steve Rogers, as comic book fans will tell you, is the alter ego of superhero Captain America. Somehow, given the evidence, that first name would have fit just as well.
Correction: Sam Shepard died Thursday. An earlier version gave an incorrect date.