Kids!!

On my journey home today on the bus whilst engrossed in my book there was a loud crash. Looking up I saw that the window in front of me had being smashed. It transpired a young kid threw a brick at the window! Needless to say the bus was not able to go any further and we were all put on another bus. The driver was telling us on average they get 11 smashed windows a day by kids!!!! My question is why?