a) The amount of my money as a tax-payer spent on the police stopping people from enjoying themselves would go down;
b) The amount of police time diverted away from stopping people harming / stealing from other people would be reduced and the detection rate for real crimes would go up;
c) People would drive more safely;
d) Recent improvements in indoor air quality would be upheld;
e) The Treasury would gain shedloads of badly needed extra cash!