Thredup/Grailed/TheRealReal/Etsy/Rent the Runway are bigger companies in that business.
Amazon also sells 'Warehouse deals' of returned product at a discount.
There are also chains of 'buy/sell/trade' stores like Buffalo Exchange, and many local vintage and consignment stores.
But there are significant challenges when you introduce all the ways that used products can deteriorate, plus the challenge of discovery and managing a stock that can potentially include 'everything ever produced in history' rather than 'this season's SKUs'. Plus the 'Market for Lemons' issue that many people generally get rid of things when they've failed somehow, and only sometimes is the issue 'I don't like this thing's style anymore'.
I generally thrift & vintage stores more interesting than new clothing stores, and enjoy the thrill you get when you find something you could never find new for a very good price, but the tradeoff is that it takes significant effort to find clean reliable basics in your size in the used market, as people generally keep those things until they wear out, and it's basically impossible to keep a full size run of anything used in stock.