Its not candy or sweets per se, its the fact the states have made it so that parents cannot discipline there children without fear of reprisal and that teachers cant do it either.
And add to that the incidences of of parents who've discovered they can sell their kids' medications (or take it themselves), and the ones who have discovered that if they work at it, they can get their "ADHD" kids to qualify as "disabled" and pull in an extra $500 or so a month per kid and then there are the ones who are just plain lazy parents...it's easier to drug the kids than train them.
The schools don't complain, because the teachers get more compliant subjects who are much easier to program and the adminstrators rake in the extra cash for all those "special needs" classrooms. Of course, when the kid turns 18 and his drugs are cut off and he starts to self-medicate, we charge him with criminal behavior or toss him in rehab for his addiction.