IMO the motown family was really a concept pre WDOLG. in those early years, where most of the artists were trying to make a hit and you had the formation of the groups, that seems to be where this "bond" really took hold. You had a group of young adults singing, making a little money, getting some fame, hooking up, being creative, etc.

in 64, the Supremes exploded onto the scene and essentially catapulted over everyone else. they now had the major bookings, the tv appearances, this mega projects, etc. WDOLD and the early Sup hits helped to establish and define the concept of "The Motown Sound." HDH and others took these early songs and patterned hit after hit on this.

And the Motown Revue was less of a focus as The Supremes and the other top acts became huge concert draws on their own.

Most of the bio books mention how crazy busy every group was by the later 60s. Otis says he rarely was able to be with the Sups and Flo since their tour and concert schedules conflicted.

then with Flo's departure from the group and label, you had a situation where someone you were once somewhat close with is no longer around. her personal problems also compounded the isolation - she shut herself off to some degree. and people had moved on with their own lives and careers. she then died 9 years or so after leaving.

If you think about where you were in your career 9 - 15 years ago, you probably had some people you hung out with, had lunch with, regularly went to happy hour with. but if you then got another job, moved to a different city, you may or may not keep in touch. Facebook and the like have helped greatly in keeping in touch. but i someone you worked with and were decent friends with 15 years ago passed away, would you go to the funeral? maybe