That's because Grand Avenue is where people go who actually want to look at art instead of be seen by other hipsters and douchebags.
First Friday has grown out out of what it used to be, and that is an art festival, into a congregation of underage binge drinking, of age binge drinking, pompous hipsters who want non-hipsters to see them looking "cool", and a few sophisticated types who actually want to look at art, and they stay far far away from that clusterfuck on Roosevelt.
scottsdale old town walk may be more the flavor for art then
We are definitely going this Friday. Will be getting on the light rail at 3rd Ave & Camelback around 7 pm, then riding down to Roosevelt where the hilarity shall ensue. Fun costumes highly encouraged.