why not just tip them in cash?
(well, not my UPS guy, he's actually a she, and she gives my dogs treats when she sees him)
People steal Amazon packages regularly, I think they would not hesitate to steal something that says "Instacart" on it.
/s but only kind of.
Besides, I don't want to have to keep a supply of small bills around just to pay a tip that I could have just put on my credit card. I rarely pay in cash these days (even pre-covid)