I don't have an answer I'm afraid, I see you've been waiting some time for it and it's an interesting question.
I suppose it was a 'safer' progression from sunbeds etc and cosmetic companies wasted no time in developing those awful smelly orange creams of years ago. (thank goodness for todays products) I'm more interested in our fascination with being tanned in the first place. We think it makes us look healthier, or even slimmer. Coco Chanel herself started it apparently after exposing herself to the sun too long accidentally. I've visited China where traditionally you're seen as poor if you have a suntan. They think you must have an outdoor job, working in farm fields etc, whereas pale skin means you spend more time indoors, either through a better job or not having to work at all! (Geisha are Japanese, but the white faces are the same concept) Pale is more attractive to them. And big backsides are more attractive in the West Indies seemingly, so maybe there's hope for me yet!