In the United States, at least, a great deal of people's self-esteem tends to be caught up in their ability to feel that they are successful. Success tends to be defined in terms of money and work status. Because of this, the lack of ability to move up in pay or work status might well constitute an emotional challenge to people in low wage jobs.
A person in a low wage job has very little ability to move ahead in ways that would give them more prestige in society. Therefore, they have to resign themselves to the idea that other people in society might see them as underachievers. This is likely to be an emotional challenge.
Since our self-esteem is often linked to our status in society, and because our status is often linked to our wages and our job status, low wage jobs can be a source of emotional challenges.