I have a condo in Vegas and have lived there many times; I can't speak at all for the other countries. Prostitution is legal in Nevada on a county by county basis. Currently twelve counties allow prostitution but only eight have operating brothels. Since prostitution is not legal in Clark County (Las Vegas) every prostitute there would fall under the illegal, hidden or street label.

I would blame a population and tourism explosion (over the last thirty years) as the reason for an increase in illegal prostitution, not that prostitution is legal in outlying counties.