Who needs to replace a car door handle? Almost no one. If you do, it's easy to go to a pick and pull junkyard to get one. If you are making new car door handles, and have to widely distribute and store them so they are available for the few people who need a new replacement, are you going to sell at a low markup or a high markup? Being cheap won't attract pick and pullers. A low margin won't convince stores to stock slow selling parts.

And if you run a restaurant, do you really want two soft drink delivery services coming in while your staff is doing food prep? Do you want to make space for two fountain machines, double sets of replacement canisters and twice as many possible customer problems with bad mix settings, running out of syrup, etc?