Instacart is being miserly by not paying their workers a fair wage.
Instacart is paying their workers fairly. It's just that the driver is not an Instacart worker.
They're not employees, they're contractors. And when you, the customer, place an order, they are now your worker as you've entered into a contract with this person. They aren't working for Instacart or the store, they're working for you. And you're the one who pays for their time and labor, that all comes out of the service charges on your order.
That's how all these apps work. They don't get paid anything by the app, they get paid by you through the app.