Or, and hear me out.
Having the proof of a possible offence, the name and address of the possible offender and having it all in one go that takes 5 minutes to deal with is somewhat easier than locating, witnessing/getting proof of the youths causing "trouble", then identifying them and dealing with it, especially as a lot of the time people complain about "youth's causing trouble" it's nonsense*, not to mention entirely different departments with entirely different man power and legal powers and depending on what sort of "trouble" they're causing it could be something that is dealt with by any of about 4 different council teams or even the police.