There a very large black population south of Boston with Bridgewater Holbrook Avon Milton Stoughton all have black populations ~12-15% now as well as Brockton being 48% black, Randolph being 40%+..the audience is there I guess the market isn’t. Remember the station only left an Urban format after iHeart took over. Execs at Greater media specifically said Boston should have an urban outlet In the press release when they debuted. There will be more attempts at Urban I’m sure. A Latino station will also come soon-just a matter of time.
Stations don't look at individual towns, cities and villages or neighborhoods. They look at the entire radio metro (often different from the government / Census Bureau / OMB definition of metro) and determine what programming has an opportunity of being profitable.
The major factor is what share of 18-49 or 25-54 (or some subset advertisers buy against) will the station be able to get if successful and in the current competitive environment.
Without getting into Urban, which seems to be your kindling point, I can mention that "Latino" is not a format, not even an ethnicity. There are many more formats in Spanish than in English because there are so many different cultures, races, ethnicities and nationalities that have created dozens of formats. While only a few are viable in the US, one that many will like, many more will not. So if someone wants to do a Spanish language format, they will know that half of Hispanics don't use Spanish radio in most markets, and the remaining half is divided into at least two or three very polarized format preferences.
That is just an example of how programming is based on more than 12+ shares and the population of a few neighborhoods.