I don't think $7 is a particularly hefty fee. If it's a grocery store they typically aren't paying employees to do shop for you, it's an extra service for an extra charge. I think I pay $10 per order from my local grocery.
Walmart's not going to be a good model, there, as while the chance of abuse being the cause might not be 100%, it hangs out near enough 100 to know more than a few intimate things about it.
If you're asking someone to collect your groceries, maybe pay them to do so. Tips are broken as a concept, so whatever there.
typically aren’t paying employees to do shop for you
The employees are paid hourly to be at work and do what they're told, basically. It's not like asking an employee to pick groceries for an order costs the company extra. The employee is already being paid to be there whether or not they pick your order.
The fee is being charged because they know you will pay it, not because it's an extra cost.
i don't know about this place but i know with a lot of other delivery options the "fee" does not go to the employees, it's just extra money because they can