They do, but it's still extremely unlikely that outdoor labourers are getting insufficient vitamin D.
The problem occurs when people in the same ethnic groups (with the same dark skin) start working indoors and actively avoiding sunlight (often because light-colored skin is seen as high class or aesthetically pleasing).
The problem occurs when people in the same ethnic groups (with the same dark skin) start working indoors and actively avoiding sunlight (often because light-colored skin is seen as high class or aesthetically pleasing).