https://www.bournemouthecho.co.uk/uk_national_news/18041901.quarter-do-not-know-bank-card-pin-heart/
I can remember mine easy. (pay at pump, cash machines and chip and pin only reader in the village shop)
I understand for people that don’t drive and live in a city could probably live without knowing it until SCA came around.
I was much more confident in remembering pin numbers before I started using contactless and google pay, and that was when I was with a bank where I just used the random one they sent me.
1234
Wow! Coincidences do happen!
I just write it on the back of the card in gold pen, that way I can remember it always. 
Why don’t people change it to part of their phone number or memorable date or time?
I guess some people don’t have any imagination.
Because many people don’t realise you can change it.
Anyway, write it on a piece of paper in nice big numbers so you can easily read it whilst standing at the cash machine, always worked for me!
I remember all my PINs, but not necessarily all the numbers.
I don’t know how people get through life to be honest. The fact it’s changeable is only written on every letter enclosed with every new card and PIN.
In the 1990s, Midland Bank Live Cash had something called PINsafe – a credit card sized grid of the letters of the alphabet. You picked a four letter word and wrote your PIN under the letters, then wrote random numbers under all the other letters. Simple but effective.
I’ve got the not-so-secure habit of changing my PINs to the default PIN of the last card I’ve received, with separate PINs for my credit cards and my debit cards.
Why isn’t that secure? As long as you don’t tell anyone it’s fine. My PIN at my legacy account hasn’t changed in decades, because it just rolls over.
That’s given me an idea. Write “Your PIN is 9465” on every ATM. Eventually, someone will arrive with that PIN. Imagine their confusion.
When you put it that way, I’m not even sure where I got that idea from. I guess it just feels “too easy”, in that once someone figures out the PIN to one of my cards, they have access to all of my debit or credit cards, depending on which one was captured. But yeah, at the end of the day, if it’s not something someone can make an educated guess on based on my social media or other personal info it’s reasonably secure.