Im 28 and have a vague recollection of cheque books. I can assure you no person under 21 in my country can say they have actually seen one. Do they still exist?
They are quite common in the U.S. Vast swaths of our financial system are still stuck in the mid-20th century or earlier. A check is the only way (besides cash) to transfer money in the U.S. without incurring some sort of fee or other overhead.
It must be because I live in a developing country or maybe the lack of infrastructure 30 years ago means we can hop and skip straight to almost fully digital. These days going to the bank is akin to corporal punishment. Just give me an app or you're dead to me.