Just thinking what 'I' did as a child, played in the park at the back of the house or went fishing in the Rec, went to chapel twice on Sundays, tin can lurky, hide and seek, hopscotch, spinning top, hoola hoop, snowball fights, roller skates, bike, on dark nights we played board games with friends or listened to music. Didn't have any youth clubs back then --- didn't get into trouble either!
As someone who is a vaguely youngish person I can say some of those activities go off the list as you hit teenager years;
Either because they're not activities seen as acceptable within your age group, which most people will avoid for fear of bullying (which is, from my experience dealt with abysmally in schools (an entirely different can of worms))
or
Because people see a group of teenagers out and about and think they're trying to cause trouble. Which is discouraging; I personally didn't like it when I was just walking to the shop with a group of friends a few years back only to be glared at by adults/elderly people who were passing by. It really does not make me feel more inclined to be more involved with society. I won't say that this is the attitude of all people, but it has been a common one that I have personally encountered.
Then again, I might just have been unlucky

I could ramble on about a few more examples but I would probably make bugger all sense!
Replying more to the main post, I know more than one person who would be in a far worse position today than they would be if the youth clubs didn't exist. I haven't been to them myself, but would have been extremely saddened to see them go.