This effect is also exacerbated in wealthier areas by bigger units. Units are less likely to seem lively because people are using a smaller proportion of rooms at any given time, and those rooms may not always even be visible to you. E.g. my grandparents flat would often have looked dark and abandoned from the courtyard, because that side of the flat was unused for much of the day, and often only lot when the curtains were closed, even when they were home and had visitors and a full house.