Where in the past the fragrance industry was terrified of launching more than a single fragrance at a time for fear they would cannibalize one another, the new strategy — at least at the artisanal end of the market — is to introduce a collection of anything up to 10 scents at once. The switch is, naturally, being driven by those ever-demanding Millennials, who are no longer satisfied with a single, signature fragrance but instead want a family of scents that they can personalize to make their own, or mix and match depending on their mood, the particular day of the week or even the time of day.

— Women's Wear Daily pins the blame for fragrance collections — launching 3 or 5 or 10 fragrances at once — on Millenials, noting also that "the modern revival of fragrance groupings became more widespread with the launch of the Tom Ford brand" (the Private Blend collection debuted in 2007). The article is premium content, but if you have a subscription you can read more at Fragrance Companies Hope Collections Will Satisfy Demanding Consumers.