I actually worked in ecommerce, including clothing brands. In one company, we built our own bespoke ecommerce website, using third party software only for the fulfillment part. In another, we used Shopify.

Building your own is expensive, which is a stretch to cover with the margins of ecommerce and not go broke. And the off-the-shelf things are shockingly bad in their core functionality (e.g. Shopify, which may actually be the most developer-friendly and innovative, has no native concept of a color swatch that works the way you'd expect, nor does it have filtering other than by a single, painfully-manual, non-composable "tag" feature). Shopify's got a huge ecosystem of one-trick-pony "Apps" that add all the missing features, but running 50 "apps" doesn't fix things either - not only can they be fundamentally incompatible with each other, but nothing can fix the underlying deficiencies of the core data models (or if I'm being more charitable, their suitability for one's unique business domain).

> Adidas (german company, german person)

Brands fit for the country of the store. For example, you won't find anything for a tall but not wide person in Singapore, except a few special stores, that won't be Adidas for sure. Unless ordering from overseas (and that costs nice money).

Because market. 1% just isn't worth it.