I take it you haven't actually had much real experience with the criminal justice system, prissy?
My son has been beaten up... Known perpetrator, no action.
He was knocked unconscious and had his eye blacked by a boy 5 years older than him because he told him to f-off... No action.
My friend's son was attacked at knife point and had his leg broken by someone now in prison for murder... The guy was interviewed but released without charge.
My car wing mirrors were kicked off 4 weeks running... No evidence, no action.
I was burgled and had my tv stolen... No evidence, no action. (In that case, I'm pretty sure the police assumed my son was involved, so didn't bother investigating).
I had a flower pot thrown thru my window. This time, I watched it happen and recognised the perpetrator, but the police said they were reluctant to pursue without an 'independent' witness. A neighbour came forward and made a statement, so they arrested the young man. He admitted it and received a caution. But I was told I would need to take out a private prosecution if I wanted to claim any damages... So, action - but not very useful action.
I think the police often take the view that, when it comes to teenagers, "these things happen", and if they think they can avoid prosecuting, they will try.