Interesting bit of history regarding photo postcards - Link here
The Wiki entry on postcards is kind of complicated, with many caveats.
The Biden postcard is slightly weird: how many people send pictures of their families along with recipes that could feed a small Indian family for a week to their constituents ?
Mrs. Biden is rather attractive though.
Apparently, collecting old postcards is a real thing.
A year or so ago, when I first heard of Amazon Mechanical Turk, I got curious and poked around their site to see what they had going on.
One collection of tasks I found was a postcard dealer who was apparently trying to catalog a batch of old cards. He posted images of the front and back sides of a great many old cards, many of them rather faded or otherwise barely legible. The task was to read and report on some of the facts printed on the cards.
The cards typically had the publishers’ name (and often, the city) printed somewhere in tiny print, and the task was to try to find and read that, and report what it said. There was another task, again with many postcard images, to attempt to read the postmark information and report on the city and date of the postmark. Since those consisted of rubber stamps, they were often hard to read.
ETA: I think you got paid something like $0.01 or maybe $0.02 for each card.
I beg your pardon ?
I am by no means a collector, but I’ve got dozens of old postcards, mostly cats, castles or Gaiety Girls ( Edwardian musical stars mostly ). You only have to go to a book fair, and there are a couple of stalls selling them, some quite highly priced.
Serious collectors catalogue them.
There are very few things that are not collected, with entire clubs for all of them found across the world.