When I was a kid in Britain in the 1970s, these were still going strong in packets of PG Tips tea. My granddad drank gallons of the stuff then sent me albums [0] filled with a full set of "tea cards" on a given subject. I learned a lot about the space race [1], and dinosaurs, from these things!
[0] http://www.brookebondcollectables.co.uk/cardlist.htm
[1] https://www.youtube.com/watch?v=qQHTVWTIsOw