There are some cities or even countries where there is no Chanel boutique and people rely on PS to get their dream bag. I do feel there is a need for genuine and ethical PS but obviously not resellers-as @gail13 explained, there is a difference.
I mean if you can afford the bag you can likely afford luxury travel. Go to Paris and make getting a bag a memory. I do not think the majority of people need to resort to resellers or shoppers. They may choose to because they have to have the hottest and newest item at that moment.