You should know that on Instacart, workers can see your tip before accepting the order. It's functionally a bid, not a tip. I'm sure they have some algorithm for what value they recommend, but to some extent, this is the workers setting the price of their own labor. If you tip too low, you run the risk of the order not being accepted.

The fundamental situation is that delivery work is not actually that cheap, and especially given that these are lower paid workers, they're also more sensitive to inflation and so you'd expect their cost to rise more steeply than other things.