The first reason is more jobs. Many people think that sex is a part of life, nowadays there are many kinds of services, for example the technician to fix the machine that you cannot do by yourself. Prostitution known as sex service, it is like other career that selling service. It is just a one of the career that do for money. It can make women get a salary. If they willing to do, It should not be any more illegal than another career. So prostitutes should have liberty to make money any way they want to.
The other reason is less sex crime. There are many sexual violence, but the big one is rape. Legal prostitution could help reduce the level of rape. This is because of the fact that some people have a lot of trouble finding sexual affairs. It is about human trafficking too. Nowadays woman is forced to be a prostitute because prostitution is differ from other profession it cannot advertise for find an employee. So if these people could pay for sex instead of forcing women to have sex for satisfy them, sexual violence would certainly decrease.
The last reason is to reduce Sexually Transmitted Disease. The one of the causes of STD nowadays is from prostitutes. If prostitution were legal the government could require health checks for prostitutes so they would not spread the disease to their customers. If it were legal there are so many rules, for example to wear a condom to protect the danger that