Rulfo does have a few of his subjects address politics in a vague, general way, but he doesn't make any direct comment on Mexico's class system or the circumstances that have led people to take these dangerous, low-paying jobs. Instead he follows one subject to a rural horse-racing competition and allows another to invite the camera into his home, and generally treats them as real people rather than tools for making statements.
That also means that the already short feature ends up with plenty of padding in the form of long, ponderous shots of Mexico City traffic, which eventually get a bit repetitive. What's in between them, though, is quietly insightful.