Most of what is termed ‘sink estate’ up here is cheap, pre fab or semi permanent housing thrown up quickly in the 60s and 70s to provide for a fast growing population when old terraces were cleared. Often built on land surrounding tower blocks, these communities usually have a central row of shops, pub, school etc and are quite closed off from surrounding areas. Predominantly council housing when built, a lot of the property is now owned either by residents (fiercely proud IME) or private land lords (dont care much ime). Cheaper housing and unscrupulous land lords leads to councils moving difficult tenants in and also means large family groups can live close together (often on the same street).
These areas generally have higher than average unemployment and substance misuse (often related) and this is often multi generational. Mental health problems, heart disease and breathing problems also have higher incidence. In Leeds, these areas are often very white.
I imagine the term sink hole is derogatory, suggesting that that is where all the acumen and muck gets caught.