This is typical of many delivery services. Your credit card support team typically wouldn’t be aware of the reason, unless the person uses the service themselves. Support Team members can’t really see the pending charges until the merchant finalizes the charge.
>>Why is there a temporary authorization placed on my card?
We place a temporary authorization hold for a slightly higher amount than your estimated order total. Authorization hold amounts vary but are typically calculated at about 115% of the order total and rounded to the nearest $5 increment. This small difference accounts for potential changes in the final total due to added items, items replaced at a different price, and the actual weight of items. You could see more than 1 authorization hold on an order if adjustments made after checkout exceed the original authorization total amount, or if you place the order several days in advance of delivery and the original authorization hold expires prior to delivery.<<
https://www.instacart.com/help/section/alcohol-free-delivery