This question is based both off a reference I just read in the Daniel Penny thread and a concealment video I recently watched that got some hate for recommending hoodies as cover garments because they might make you look gangster.
I think the answer might be "both", based on geography, culture, and maybe age. I rarely wore hoodies back in California, but they were pretty mainstream with the surfer dudes, and my now mid-40s Calif Nephew in law has never been seen by me without one on any day below like 80deg.
Here in Idaho - and the concealment video I watched was made by an Idaho holster maker - they are absolutely mainstream across demographics. The young guys (and gals) wear them; 90% of the tradespeople wear them; farmers wear them. Even older guys (I'm only 30 though) like me wear them. My farm coats are almost all hoodies, I'm sitting here typing while wearing my Deus Vult sweatshirt hoodie, and I'll be wearing it with a pistol underneath when I hit the German store for Xmas food in a couple of hours.
Hoodies have become my #1 concealment garment for 2/3 of the year here, and they certainly seem mainstream and "blend in" to me. Other than I guess you might not be grey man in the gun culture, because pretty much every customer and employee in my LGS also wears hoodies most of the year. I find them really good for concealment, and very easy to clear when I draw appendo.
So anyway, I have seen them as mainstream in the Calif coastal dude crowd, and across demographics in Idaho. While they might certainly be an indicator of gangster to me here, it would have to be coupled with other behaviors by the wearer. I don't know enough about places like NYC or Bogie's auto parts store to know if a hoodie alone is a major indicator of gangster.
Anyways, just curious.