From a Smithsonian article about the regulation and taxation of prostitutes during the Civil war in a successful attempt to reduce the spread of disease among soldiers:
-- ...by early 1864 some 352 women were on record as being licensed, and another hundred had been successfully treated for syphilis and other conditions hazardous to their industry. In the summer of 1864, one doctor at the hospital remarked on a “marked improvement” in the licensed prostitutes’ physical and mental health, noting that at the beginning of the initiative the women had been characterized by use of crude language and little care for personal hygiene, but were soon virtual models of “cleanliness and propriety.”
...the expenses of the program from September 1863 to June totaled just over $6,000, with income from the taxes on “lewd women” reached $5,900. ...the Pacific Medical Journal argued that legalized prostitution not only helped rid Rosecrans’ army of venereal disease, it also had a positive impact on other armies...
Today, the handful of U.S. counties that allow prostitution, such as Nevada’s Lyon County, rely on a regulatory system remarkably similar to the one implemented in 1863 Nashville. --
So, a great success in cleanliness, health, disease prevention, and public safety; all obtained at virtually no net cost to the government. Since common sense is virtually nonexistent, don't expect our current governments to stop encouraging filth, illness, the spread of disease, and public danger; all at great financial cost. That's because these things are all moral.