We don't find it amusing because we have respect for ourselves and for society. They do not. They have no discipline, not at home, not at school and not on the streets. These kids spend a regular night roaming the streets, looking for trouble, causing trouble...because they have nothing better to do. Causing trouble is their entertainment, it's how they pass their time most nights. Of course there are some bandwagon jumpers who have seen this as an opportunity to pick up free things and they are getting in on the act.
I'm not saying these people don't have complaints and reason to be disillusioned, I am sure they do and many of their complaints may even be valid ones. I just don't believe it's that disenchantment which has suddenly sparked this off, it may be the reason they think this is "okay", but it's not what set them off in the first place.
For example, the steal from shops, fine, I get it, they want PS3's, laptops, whatever. But why set somebody's car on fire? Or somebody's home or business? You don't know who it belongs to. That is totally mindless.