I think the distinction has been left implicit in the foregoing between prostitution and other crimes, such as white slavery, violation of civil rights, abuse, labor fraud, coercion, breach of promise, and physical assault. These things are all crimes AND they are associated with drugs and prostitution. But this association of ideas is not a necessary linkage; it is possible that the reason these events appear in related clusters is because they are all the province of criminals.
Prostitution, despite its moral penumbra, is not a criminal act in itself, in its nature. It is a free contract between consenting adults. The criminality enters in when pimps, drugs, desperate runaways and minors are thrown into the mix, and health and civil liberties go by the boards.
Bobert is correct that of itself it is a victimless crime. The vicitimization is largely thrust on the practitioner because of the illegality.
There are other issues around the practice because it often acts as an escape from broken or dysfunctional relationships in families who should be spending that energy, one might think, repairing their connections. But so are bars, nightclubs, poolhalls, and so on, all of which serve as retreats for thos ewho cannot communicate or who have built unhealthy connections in life.
I don't think the relationship between criminality and prostitution is a causal link; I think it is a by-product of knee-jerk management.