This has nothing to do with short term memory. You only get one new word per day. You get to add it to the earlier words and spend hours practicing the new phrase, writing it out, etc. Then you go in the next day, recite it, get a new word to add on. [Edit: re-reading the original post, maybe you don't get to write it down, but that's ok].

Do you know your own phone number, license plate, birthdate, address, SSN, credit card number, and so on? Some subset of the same basic info about your friends and family? It's all pretty random and comes to about the same thing.

I do think people rely on computers and smart phones more instead of remembering stuff. I'm old, went to school before everyone had mobile phones and computers, you had a land phone at home and it didn't store any numbers-you had to manually dial them. So you used the phone a lot more for stuff that you'd text or email today, and you'd manually dial the number. After you dial someone's number a few times you'd remember it. So you probably knew a few dozen phone numbers by memory. At best similar to a comparable number of words.

Also, maybe more people are having trouble. Microplastics? Covid? Who knows. https://medicalxpress.com/news/2025-09-sharp-memory-problems-adults.html