Hollywood serves as the backdrop and the "lifestyle" serves to create plot points and situations that the characters must deal with. The portrayal of the industry and of the scene swings back and forth between glamorizing and satirizing (with earlier seasons being more towards the former and later seasons more towards the latter).
The point is really about the relationships between friends and the way each grows and deals with changing situations. What draws you in, on SOME level is the fantasy of living that lifestyle--but ultimately, it's not relateable and you'd lose interest. What keeps you coming back is internalizing the interactions and deciding how you'd act in those situations.
Even if you can't relate to figuring out whether XYZ movie would be a good fit, you can understand job trouble; or living in your brothers shadow; or being too into your job.
In most groups of friends there's that one guy that seems to have everything come easy to him, and everyone else is sort of a planet to his star. The show explores a lot of that.
This was all done in much the same way as Sex and the City. Manhattan was the backdrop, sex and relationships as talking points.
I don't think the average woman in Oklahoma could relate, but the draw was the conversations and friendships between the characters, which are in some ways universal.