>>6855944Because the OP set only has female minifigs.
Let's be entirely honest, the main reason the set might be shelfwarming is because of the price and because of the very specific niche it appeals to.
When I say niche I'm not talking about "m-muh SJWs", but people who like to collect Lego that is just meant for display purposes.
It's the exact same reason as to why you see Architecture sets stay very long on shelves. Even though I collect them, I'm aware that they're overly expensive (due to licensing) and don't offer any play value.
Is this set trying to promove Diversity(TM)? Yes. But the main reason people don't want to buy it is because it's three little shelfwarmers that cost more than they should and that aren't as interesting as, say, the Saturn V set.