In those situations, dirty nails are not a sign of carelessness. They are a sign of work.
Context Changes Everything
The same detail — nails darkened with dirt — can mean completely different things depending on the situation.
At a formal dinner with no sign of labor? It might suggest poor hygiene.
At the end of a long shift on a construction site? It likely shows dedication.
During volunteer work cleaning after a flood? It reflects service.
On a parent who just repaired a broken fence? It shows responsibility.
Without context, judgment easily turns into assumption.
damaged damaged nail without manicure with dirt close-up. Nail Health Care.

For illustrative purposes only
The Deeper Question
So what do you call someone with nails like that?
There isn’t a single fair answer.
You might call them: