Amazon Purposely Delays Shipping

I've noticed a pattern with Amazon delays lately. Whenever I have a package that is supposed to arrive on a particular day (let's say Friday) and I also have a package being delivered the next day (Saturday), the Friday package always gets delayed so that Amazon drivers only have the one delivery. I have an important car part that I ordered Wednesday (in-stock) scheduled to be delivered today (Friday) still sitting in our local Amazon warehouse that is rescheduled to be delivered tomorrow (Saturday).