There are a lot of wealthy retirees in South Florida who make great marks. Beyond that it’s probably to some extent driven by talent agglomeration effects; if you’re someone who makes their money promoting scammy penny stocks, you might want to learn from other people who promote scammy penny stocks, so if they’re in Boca, you’ll go to Boca. Coincidentally(?) Boca Raton was founded by the Mizner brothers, Addison and Wilson; Wilson Mizner was himself a notorious con man.