There have been studies of clients, including by some of my own colleagues here in Canada, and also a fairly large study of clients, or people who buy sexual services, in Sweden after purchasing was criminalized. Those people reported in those interviews that they were less likely to come forward with information about someone who was being forced into prostitution or being held against their will, of course with legitimate reasons; they feared they would be arrested for purchasing.
In Canada I think we have the same situation where people are now fearful to come forward. It's the same with people who operate an escort agency or a massage parlour. If they see something, it's very difficult for them to come forward at this point, given our law.
There could be practices even now where we give an amnesty for coming forward with information about illegal or especially human trafficking activity or a minor being involved in sexual exchange. I think clients and other third parties would be much more willing to come forward with information if they knew the justice system would not criminalize them. That would also be for sex workers themselves, of course.