This 2010 article in The New York Times includes a conversation with Charles Portis, the author of the novel on which the movies were based:

Portis’s characters have a self-conscious manner, a homespun formality of speech, that comes from the effort to inhabit grandiose roles: lone avenger on a quest; nefarious outlaw; besieged moral exemplar. If that sounds like a description of Cormac McCarthy’s characters, the great difference is that Portis finds comedy in the aspiration to heroism, and his characters are forever plagued by a suspicion of their own ridiculousness.

Portis, who died in 2020, was called reclusive, but it seems more likely that he just didn’t like self-promotion, doing interviews, publicity, celebrity and the other trappings of fame.

The Washington Post describes how Portis became a writer: It started when he attended college after military service.

“You had to choose a major, so I put down journalism…. I must have thought it would be fun and not very hard, something like barber college — not to offend the barbers. They probably provide a more useful service.