Grocery is like health payers, 8 or 9 old legacy systems that have never been upgraded and are held together with duct tape. Until this changes, Instacart and similar are at the mercy of what they can find on the shelf when they send a body to pick.

Instacart has other issues similar to Uber. They have updated their app, basically removing / hiding drivers tips and replaced the field with a service charge. This is an will cost them drivers along with customer loyalty.