The deterrents are too low. You can get as little as 10 years for murder, serve much less. If someone you knew got banged up for life then I reckon you'd think twice about copying what he did.
That said there has always been plenty of violence on the streets. I always avoided skinheads when I could. Teddy boys were a threat from what I've read. Victorian times, the 30s, it's what was done to perpetrators who were caught that stopped things being worse back then.
Could be we are just an unpleasant species.