I'm 65 and I've written hundreds, probably maybe thousands of cheques over my lifetime, monthly and quarterly bills for example, or when shopping with a cheque guarantee card. I remember when the supermarket in Hammersmith started accepting credit cards in 1982, so that became my preferred payment method from then on.
But maybe 3 in the last 10 years, one for Companies House (£10) and two for debt collectors who were chasing me for payment to insolvent energy supply companies, so in the latter case a cheque with a second class stamp seemed the best option.
I've sent large amounts of money to people who invest money by cheque in the past, but last time I just sent it online at £20,000 per day which was my limit until it all got there.
I've also received refunds from British Gas and Royal Mail by cheque, presumably also on the basis that it slows the process down, but I'm now able to pay these in online I'm glad to say. Shred the cheque once the money is confirmed in my account.