There's been a few features on BBC London news over the last decade about the numbers of youth clubs that have closed in London, especially those setup in the most deprived areas. They often had ex offenders running after school music and sports clubs etc and generally gave a lot of these kids someone to look up to (since there seems to be a huge number who have no male role model in their family). That along with massive cuts to social services etc will have all had a significant impact. Then again we often see an increase in crime in tough times and I suspect it doesn't help one iota having governments and the rich clearly seen to prosper with highly dodgy and at times illegal activities themselves and seemingly get away with it.. so why shouldn't I mentality comes into play. Especially towards what they see as larger corporations.
Then you've got the massively negative part of social media which helps organise, a certain portion of some music which massively glamorises violence, drugs etc and we're living in an age where people just don't care.. and just aren't caught. They know cameras are everywhere but put a hoodie on, cover your face and you're unlikely to get caught.
You need to give people something to live for, something that's better than that. In inner cities, gangs replace familes and if you remove all the support structure that was put in place to try and give people an alternative.. why are we remotely suprised when crime then rises?
Put back that support structure, put back local community policing (who generally get their area), get more Prison spaces (seems we've run out and are letting people out early) and maybe you'll start to see some progress. Otherwise I fear it's only going to get worse.. just throwing xx Police at issues with no other plan (when the government cut tens of thousands of them, along with Police stations) won't do much.