“If millennials are digitally savvy, then Generation Z are total digital natives,” Ms. Greene said. “They are completely au fait with the internet and social media platforms, and comfortable using them to create anything from fan forums to charities and their own minibusinesses. Their identities are defined by their interactions and relationships online, both with one another and celebrities.

“That’s why stars like Kylie Jenner, who interact with them like peers on the mediums they feel most comfortable with rather than more traditional retail platforms, are seeing such astronomical success.”

Some independent businesses are also recognizing new opportunities to profit and are building new services accordingly. Depop, which was started in Britain in 2012, is a buying, selling and swapping app for clothes, accessories and other wares. It created communities of influencers and like-minded shoppers and has strong roots in the resale market. Eighty percent of its user base is under 30.

“Brands like Supreme and Palace really understand successful 21st-century branding and how to appeal to younger consumers from the selfie generation,” said Maria Raga, the chief executive of Depop. “There is no question that our business is capitalizing on their success. Many of the most successful resellers to emerge out of the drop culture don’t just see what they do as a way of making money. They see it as a way of building their own brand. They can gain huge profiles and followings in their own right.”

It’s not necessarily in their nature to save the earnings from transactions either. “To keep up their social media credentials, Generation Z feel they need to change their clothing much quicker than shoppers in their late 20s upward,” Ms. Raga said. “Plus there is always a hot new pricey brand on the up. Most of them are students. They aren’t really earning money yet. So to buy more, they need to keep selling stuff.”

Charles Fitchew, a 13-year-old in Manchester, England, is one example. He said he did 95 percent of his shopping online, with the traditional majority of any new purchases coming from drops. Lately, however, he said a growing number now came from transactions that took place on Facebook messenger chat groups, particularly for sneaker resales, which tend to be dominated by young men. (No surprise: Kylie Jenner’s sales are predominantly driven by teenage girls and women in their 20s.)