This is because sex work is a choice and it can protect women from abuse and violence. This will happen because prostitutes are not likely to report abuse and violence to the authorities when it happens but if we legalise it, it can give women more rights and encourage them to seek help if any violence or abuse happens to them. If it were legalised then a women could call the police for help if they need it. Also what adults do behind closed doors, whether they pay for it or not, is no concern of the state.
The argument against this is that prostitution is violence towards prostitutes. Regardless of prostitution's status legal or illegal or its physical location strip club, massage parlour, street, escort/home/hotel, prostitution is extremely dangerous for women. Homicide is a frequent cause of death. It is not true to suggest that legalization will protect anyone in prostitution. It is not possible to protect someone whose source of income exposes them to the likelihood of being raped on average once a