I would argue that the reaction to 9/11 empowered the state to terrorize parents for just about anything. The risk of a confrontation with police has escalated in the past two decades, such that any report is taken seriously and without any real consequences for making false reports. Couple that with an increase from meddling by busybodies that can report free ranging kids using their now ubiquitous cellphones, and parents quickly realize that it is safer to keep them at home.