Puzo presents that level of detail about the Bocch because they otherwise have no explicit or assumed role in the novel. Also, it's an interesting departure from the usual and customary story about Mafia families. Stracci and Cuneo, however, fit the usual and customary mold of Mafia families, so one can make certain assumptions about their nefariou activities that realy don't require more than a paragraph or so.

In fact, Puzo goes out of his way to say that the Bocch had a streak of stupidity, their lack of adeptness at traditional Mafia endeavors, and their embrace of what is essentially a passive criminal role.