I would say it is more this.
People are cowards.
I was surrounded by a large gang when I was young, and despite it being in the main street in the middle of the day, with plenty of people around - not one person intervened.
They even moved away so they wouldn't have any spillover.
This was a gang of 16 year olds for the most part, about 20 of them.
Eventually we pushed through when my friend's father arrived.
He saw what was going on, jumped out and confronted them, then shouted for the police to come - who were a few yards away.
No idea if the police had seen before, but the police are also fucking cowards in general, and won't approach any group unless they outnumber them.
Society didn't used to be like this, from what I can tell. There would be men who'd stick up for people who were in trouble.
Another time, a group of 18+ year olds surrounded us, while we were several years younger.
Middle of the day in the park, intimidating and threatening us.
Then to our relief, two men came up and said "what do you think you're doing, picking on kids" - and scared the shit out of the 18 year old faggots.
That's the kind of response there should be. It doesn't take much.
If you personally see anyone who isn't in a good situation and is outnumbered - shout something or phone the police and make it well known that you have phoned them.
Don't put yourself at risk, but do something right away - don't think that someone else will take care of it. Encourage your friends to do the same. People will remember you for life for helping them out.