So the way that this works has nothing to do with user experience. A long while ago, USPS automated the mail sorting at their distribution centers by taking photos of the mail. Anything that could be sorted automatically was, anything that fails falls back to humans to sort.
Someone over at USPS had the brilliant idea to save the photos they were taking to sort the mail anyway and email it to people at the addresses that the mail was being sorted to, and to do it for free.
It's basically repurposing a critical piece of infrastructure to give you a little QoL bonus with your mail, and we should be really thankful anyone thought to do it instead of complaining about what's lacking. Especially when policymakers use every attempt to defund it so they can get their ultimate goal of privatizing mail and package delivery.