I consulted with some nice producers today who had a series idea they wanted some feedback on. The pages described in great detail a setting and some characters, but what it didn't have was what pros in L.A. call "the franchise." Despite knowing where it took place and whose stories I'd be tracking, I couldn't get a handle on the show itself because it lacked the basic definition of what an audience could expect to see week after week.
It's that franchise that distinguishes, for example, the series Degrassi and 90210. Both are set in high schools and have teenage characters. Yet, their respective audiences, (or even if their audiences are the same), know the difference between the shows. They know that when they tune into Degrassi, they're going to see teen characters coping with edgy, highly charged issues like homosexuality, drugs and pregnancy. When they tune into 90210, they're going to see very different teen characters, primarily because they're rich and live in Beverly Hills, in very different stories.
It's hard for an outsider to define the franchise, but the creator and presumably the broadcasters understand what the franchise of their show is. And it's the delineation of that franchise that then defines things like setting and characters. You know that 90210 needs a "good" girl character and a "bad" girl character because of the franchise, which is not about exploring social issues like Degrassi does, but more of a teen soap. Thus, it's not an accident that 90210 is set in Beverly Hills. It would be ludicrous for a show set in Beverly Hills to do an episode about a homelessness, for instance, but a homeless teen student would be entirely plausible as a Degrassi character.
The clarity of the series' franchise will affect EVERYTHING. The value of clearly defining a series franchise is that creative choices do not become arbitrary but become focused within the venn diagram of the franchise. Anything that sits outside the franchise of the show doesn't matter. Franchises define setting, characters even titles.