This might sound a little harsh but...
I think a lot of it is the parents. Today's young parents seem to be doing everything in their power to be different from their own parents.
As a result, today's kids are not as disciplined, and some parents even make excuses for them, saying they "can't help it" when they actually can. Of course there are those children who really can't help it, but for the sake of this question, I'm speaking of the ones that can.
Today's kids are cruel and selfish. And lazy to boot. They want their parents to give them everything they want, and a lot of them do just to avoid confrontation. There can be any number of reasons why they would avoid putting their foot down. Maybe they just don't feel like dealing with them. Maybe they have run out of ideas and given up. Maybe they are scared that they will be too harsh. Who knows. But I do know that everything starts at home. And whatever starts there feeds off of the outer environment.