> Dealers have inventories - they purchase items from the suppliers and resell them - if they misjudge demand, they're left off with useless goods.

Everything is negotiable. If a retailer has more power than a supplier, then the retailer can demand a guaranteed sale clause in the contract, requiring the supplier to take back unsold goods and refund them.

https://www.comcapfactoring.com/blog/walmart-vendor-financin...

https://factor-this.com/walmart-supplier-financing/

The major brick and mortar stores are not solely dealers, they often have various deals where they sell items on consignment and do not pay for inventory until after they're sold, require payment for "shelf space", etc. That's transparent from a customer perspective, but from a supplier viewpoint they're often quite close to brokers in practice.

The consignment model and paying for shelf space are the exception in retail though, not the rule.

They tend to exist only where there is a huge asymmetry in power between retailer (usually large chains) and suppliers.

Isn't most of retail done by large chains with a huge asymmetry in power?

Depends on (1) what country/region you live in and (2) what brand you're talking about. For example: Yes, Safeway may be huge, but so is Procter and Gamble. Is there an asymmetry there? I'm not sure.

Anyways, large chains don't deal exclusively in consignment either.