In all serious though, it just gives the police the legal power to do something before actual trouble starts. You're not going to go to prison for spending to long sitting on a park bench!
True. And its also used to sanction ppl using "code words" to try to commit victimless crimes. For example, based on when I lived in NYC:
The ticket scalpers outside Madison Square Garden wouldn't call out that they
were selling tickets, they'd act like ppl trying to buy tix (saying "who's selling tickets", etc. as their calling card).
The hookers working the streets wouldn't offer sex, they'd say "you going out?" or other innocuous questions. Which were also a "calling card".
So were drug dealers saying "Smoke, smoke", etc. (who'd signal a runner to bring whatever when they made a sale).
Maybe the words have changed in the quarter century since, but the point is the same; and they authorities use the rather murky "loitering for the purpose of...."
(the presumed intended act) to enhance the fine for loitering.
Of course the cops knew exactly what was being communicated, but entrapment is illegal (not that it isn't done, especially putting those thought to have terrorist sympathies up to stuff).
The loitering statutes are also used to "crack down on" the homeless. On this point I'll bash the NY Civil Liberties Union though, as a lot of the homeless on the streets clearly needed help (involuntarily if necessary, IMO) but civil liberties lawyers living in fancy digs were quite ready to defend the "right" of ppl 2B homeless vagrants for years on end.