Take all your mail, then rifle through it looking at the postage. Make a pile for Standard, a pile for First Class, and put everything else in a third pile (non-profit etc). Look through the pile of Standard. It's literally all garbage. Look through the pile of first class, them's the bills. Look through the non-profit pile and if you're lucky you got return address labels from the Humane Society. If you didn't get return address labels and you need return address labels, make a small donation to the ASCPA and give it a month
Given that I write like... 2 letters a year, it's really not a significant burden. Anything of consequence is online, and if I'm mailing Christmas cards or something, I'll want a festive return label anyway.
If I lived in the US I'd have liked to vote to make it illegal to deliver promotional / junk / "Standard" mail to mailboxes with a standardized and large "NO ADS" label in specified spots on the front and sides, with a small fine for the post worker and very large fines for the companies in the ads.
I would not be happy to sit and sort through piles of junk for the rest of my life, with it without knowing that "Standard" is all junk.