Customer acquisition? In some cases it might make financial sense to lose a small amount of money per customer if the cost per acquisition is more than the amount they're losing.

Network effect? I'm not sure this would apply to a clothing retailer, but there are lots of services out there that have a marginal cost per customer but can't effectively monetize until they have a sufficiently large customer base and therefore have access to enough data to be marketable.

Exit strategy? A company with x million customers, even if unprofitable and unsustainable in its current state, is worth more than a company with x/n customers that is marginally profitable in many cases.

As for this case in particular... I don't know. I suspect that a case could be made that the money they're losing has them in the media enough that they're basically paying for advertising by being unprofitable. I doubt I would have ever heard of MoviePass if not for them being constantly in the news.

Happened all the time in the dotcom bubble:

"We lose money on each sale but we'll make it up in volume!"

The CLTV is high in fashion - people return to shops they like over and over. If they're in high growth, they're spending a lot in marketing to get new customers acquainted with the brand.