No can say for certain as to the benefits.
People are already driving DUI
  Legal grugs
  Illegal drugs
  Alcohol
  Poor gene pool
  Religion
  Flat out crazier than bed bugs
  Horny

Two possibles are
Increase in tax revenues
and
A few less people on the probation roles
No can say for certain, only politicians and those that claim to speak for god would profess certainty.