Dropshipping is a great way to test an item before private labelling. Then you can focus on building that brand and not worry about being priced out by your supplier. Even DoorDash is a dropshipper since they list all restaurants on their app, order from the restaurant when an order comes, and then handle the "fulfillment" aspect.

I'm working on an e-commerce automation platform called Openship and one of our first users wasn't even into dropshipping. She sold her own brand coffee but wanted to sell coffee accessories like french presses, grinders, etc. Her buyers would get these add-ons with the coffee. She would ship the coffee and dropship the other items. Those add-ons would cover her ad costs and she eventually private labelled those items too. That is how you effectively use dropshipping to test and build out your catalog.