Agreed. But until we actually hold these giant companies accountable, please don't take it out on the worker by stiffing them. If you don't want to pay the fees, don't use that service, and tell them that.
I think of it like a bid for the work order. In fact, I think I read somewhere that that's explicitly how it works for instacart: the tip values are shown before the insta employee/contractor picks up the job, and they're encouraged to only take the ones that pay worth their time.
Then that's misleading to the customer. When you buy something online and have paid for it, it should be collected and delivered.
When you need to pay a tip to get the omployers/contracters of the company to do business with to do their job, there is something terribly wrong with the situation. Tips should be for complementing employers with their good/excelent serice, not to ensure they have something to eat while the company earns enough and underpays their staff.
That's how an open market should work, companies paying their straff living wages and charging what a product/service costs to be viable. When the product/service is good enough, the customers will come, when it isn't, they go out of business, freeing employers for work that is values correctly. The US market of underpaying employers and required tips from customers looks more like modern slavery/forced labour.