The nature of the product is important too.
Allbirds makes big products that are expensive to ship and return. Shoes is terrible as a DTC product, unlike smaller, lighter, and more profitable products like jewelry, clothes, watches, coffee, makeup, or earplugs (Loop is a great example).
Also Allbirds doesn't necessarily cater to a category of customers that would build a community around their products.
Their choice to remain DTC-only is hard to understand when thousands of brands are profitable with their own store, from Levi's to Havaianas.
The cheapest brands I know (Primark, Action, etc) don't even sell online as the supply chain + marketing costs are too high.
At the end of the day, DTC is great only for small, light, high-margin products that ensure quick repeat purchase (anything that would fit in a subscription box); it's terrible for everything else.
Even Just Spices had to sign up with retailers to achieve profitability.
Great article btw.