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.

> 1. I get the pictures DAYS before the actual mail (weekends ignored). Why?!

I'd bet it's because the envelopes are photographed in some central location, the photos get sent at the speed of light but the physical envelopes only start getting to the last mile physical delivery people after.

Indeed, there are regional sorting centers that then send to the local post offices to go to the carriers. Although what I find odd is that for residential delivery, I always get the mail the same day, only at my P.O. Box does the mail sometimes come 1–3 days later.

If you look at the email, the promise isn’t “coming today” but “coming soon”.

I think this is something that sucks about your particular sorting facility or you're just very unlucky. I've been using Informed Delivery since it launched, in two different states, and while it's not perfect, I find it pretty accurate, especially for normal mail (envelopes, postcards, and so forth). I'd guesstimate that it misses a real non-junk mail item less than 1% of the time, and it misstates when something will be delivered 5% of the time or less. Certainly not enough to offset the value of the service.