Not always necessary either. The kids probably just haven't thought about any problems they might be causing.
My ex, when he was a bobby, was called to 'vandalism' at an estate in town. When he arrived, he found two 10 year old boys, with spades, carving out a set of bike jumps on the communal lawn
The chap who had phoned in came storming out wanting the kids hanging, drawing and quartering
D placated the chap and went to talk to the kids. What are you doing lads? Well, we saw this nice flat area and thought we'd make some bike jumps for us and our friends. Well, see, you can't do that here because other people like the grass green and flat, they don't like to see bike jumps. Oh, said the kids, very surprised at this odd point of view. So you're going to have to flatten them out again. Oh no, really mister. Yep.
So D arranged to come back in an hour and sure enough, an approximate 10 year old attempt at flattening the jumps had been made.
He was laughing about it later, said they honestly hadn't seen a problem with what they were doing.
It would have been easy to call them hooligans and vandals - but they were just being kids.