Stores like Walgreens and Walmart lock up a range of goods at their stores.Lindsey Nicholson/Universal Images Group via Getty ImagesLocked-up merchandise at retailers is turning off delivery workers for services like Instacart.Shopping and delivering orders on-time is a struggle with so much locked up, workers said.Retailers from Walmart to Walgreens have items under lock-and-key in an attempt to prevent theft.Locked-up bottles of dish detergent and water at retailers like CVS and Walmart isn't just a headache for customers doing their own shopping: It's also hampering deliveries through services like Instacart.Unlike regular shoppers, delivery workers who pick up orders at stores usually have to shop and deliver their orders on a deadline.