Many Europeans seeking to explain the American obsession with counteracting all types of vice lay it all at the door of our Puritanical roots. This cannot be the complete story, however, because the Dutch have the same Puritanical roots as the Americans (in fact, the Pilgrims stopped a while in the Netherlands before sailing to America).
So, you have two countries, the United States and the Netherlands, with the exact same roots. If you consider society the "trees" they seem very similar. Both societies are pragmatic, hard working and productive. However, the Dutch pragmatism has led them to chose to divert their country's resources to important things like health care and social security, instead of chasing down marijuana smokers, prostitutes and their Johns.
Contrary to popular belief, smoking marijuana is against the law in the Netherlands (it actually has to be according to some multi-lateral treaty; which one, I cannot name off hand). However, the Dutch instead have chosen to accept that light drugs have limited affect on society overall and to regulate it. Therefore, while illegal, Amsterdam has "coffee shops" that sell marijuana (if you really want coffee, you have to go to a "cafe" or a "bruin cafe").
In addition, prositution is legal and regulated in Amsterdam. There it is, out in the open. In fact, if you wander around the Red Light District, there are picture windows with prostitutes of all sorts for all to see. No pimps, no desperation, no STDs. And here's the big shocker of it all.....
CIVILIZED SOCIETY AS WE KNOW IT HAS NOT CEASED TO EXIST.
Something to think about. I'm not saying that marijuana and prostitution are good things. However, rather than spending millions of tax dollars chasing "soft drugs" and prostitutes (not to mention the millions spent on new jails to house all those that we've designated as criminals as a result), perhaps we should realize that, despite 20 years of the "War on Drugs" and other vice patrols, it still exists. Why not regulate the behavior to make it safe instead?
Also, instead of chasing ghosts that never really affect us (I mean, really, when is the last time you were bothered by a prostitute?), perhaps we should divert some of those resources into benefits that we personally could use. Healthcare and proper care for the elderly would be a good start. I'd also toss in a vote for free higher education too.