However, i know that people felt insecure when they won big money at physical gambling casino and sometimes, they were robbed too.
I never heard of street gambling in my part of the world. Kids or some teenager may bet while playing street games but we won't call them serious gamblers.
Children or teenagers are probably the ones who most often play gambling on the streets when hanging out with their friends. And their parents don't know about it, so this can lead to gambling addiction when they are adults if their parents don't take any precautions.
This do leading to fighting that can cause the present of police to come and intervene. I can't even advise anyone to try going for street gambling because it can be very deceitful and full of evil mindset.
But I don't know what kind of street casino @OP is referring to. Is it like that or is there another form? If so, they could likely have bribed police officers or paid security to guard the area against criminals trying to rob the winners.