What's with all of the Pittsburgh references?

I am from Pittsburgh, so I noticed some things that were interesting to me.

I understand that Cal McAffrey (Russell Crowe) and Stephen Collins (Ben Affleck) grew up together and are from "the 7th District in Pennsylvania", presumably around Pittsburgh, with all of the Steelers logo cameos. But, at the beginning of the film when a co-worker calls Cal McAffrey "Yinzer" and Cal McAffrey twice calls Stephen Collins "Sliberty", who outside of Pittsburgh could possibly know what these references are?

I see that there are four screenwriting credits on this film. Does anyone know how Pittsburgh ended up to be a part of the film? I'm just wondering why these two characters' hometowns, seemingly irrelevant to the story, are referenced so often. It just seemed unnaturally prevalent in the screenplay to me...I mean the Steelers logos and the Pittsburgh references. Maybe I just noticed them more, being from Pittsburgh, I don't know.

For those who might not know and are curious, "Yinzer" is a reference to a Pittsburgh resident who most likely speaks in a unique, local dialect called "Pittsburghese", which is spoken by many residents of Pittsburgh and parts of surrounding Western Pennsylvania. "Yinz" is a derivation of "Youns", which comes from "you ones", or "you all", as in (speaking to more than one person)..."Yinz want to go to the Steelers game on Sunday?"

"Sliberty", is a reference to an area of Pittsburgh known as "East Liberty", and many Pittsburghers join the words East and Liberty together, which sounds like "Sliberty" when spoken quickly. I suppose that Stephen Collins must have been from East Liberty for McAffrey to be calling him "Sliberty".