There has been a gradual decline in bank branches for around 50 years.
It's the "last bank standing" that have been closing in lots of towns over the past few years. Most large villages used to have a branch of some bank. Small towns had branches of several banks. Larger towns would have several branches of each major bank.
My office is in a building which used to be our local Nat West branch until they pulled out in the mid 1990's and it was converted to an office with flat above.
Cheque books and credit cards really weren't commonplace until the 70s/80s. People were paid their wages in cash and paid their bills in cash. They'd go to the bank pretty regularly to put in cash for savings or withdraw cash, or pay bills. This was before the proliferation of supermarkets, so there were huge numbers of small shops and other businesses who needed local bank branches to pay in their takings etc.
Then we had a decade or two of employers moving over to BACS for payment, credit/debit cards, etc., and people didn't need bank branches as much, hence the big banks closed down the smaller branches in each town/city and concentrated on the main branch in the town/city centre.
Then in the 00's, online banking took off, and the need for the main town branches started to dwindle, so many were closed and many towns were left without a branch of the main banks.
It's been about 50 years of a move away from cash and towards online banking, with credit/debit cards in the middle, which are now starting to dwindle in use themselves due to phone apps, paypal, online transfers etc.