If you want to blame someone, I suggest looking for the actual culprit and not a law-abiding company. This has little to do with Instacart and everything to do with state wage laws.
(1) Tips are expected in the restaurant industry
(2) Waitstaff knows what they're signing up for
(3) The restaurant does not adjust wages after tips have been received
In many cases they do. If you receive zero tips for a shift, they are obligated to pay out minimum wage. If you receive $200 in tips for a shift, they pay out a lower figure, usually around $2.
The people delivering here are "contractors", not employees, so this doesn't actually apply to them; what Instacart is doing here is merely reprehensible, as opposed to illegal.
https://www.dol.gov/whd/state/tipped.htm
It is, of course, entirely possible that the worker in question is not on the west coast, but Instacart is still welcome to pay a fair wage even if not required to by law, and Instacart should certainly avoid lying about their business practices either way (from the article: "Even Instacart seems to know how messed up it is to pay workers less when they get tipped more — which is why they’ve denied the practice when speaking to reporters at Business Insider & the Miami Herald.")
The receipt was for a store named Wegmans. Those stores are located on the East coast (New York, Pennsylvania, Virginia, Maryland, Massachusetts, New Jersey).
It may be legal for instacart to take the tip money but it’s their decision to do so and they deserve the blame.
It’s wrong because the people paying the tip generally believe it goes to the person providing the service, not to the company. And it subverts the purpose, which is to incent and reward good personal service.
So the company ends up screwing their workers, deceiving their customers and disincentizing good service.
Legal, but wrong and stupid.