This is a surprising question in that many people seem to be asking the very same thing. While there are mixed feelings about it, the move actually makes perfect sense in today’s economy. The smaller denomination offers a bit more flexibility for those of us using cash machines.
There is no real rhyme or reason behind the move other than to give depositors additional options when using a cash machine. Instead of receiving only large bills, customers can now make smaller withdrawals if they wish, assuming the bank limits for cash machines are lower, and not have so much cash in hand.
If they need to pay for something in cash that costs less than £20, they will not have smaller denominations with which to work.
Something else to consider is the need for less change when making a transaction. Think about how many times you have been to a street vendor or cab driver that did not have the proper change when presented with a big bill.
Personally, this is a welcome change as it will be nice to have some smaller bills in my wallet when making a cash withdrawal for cash transactions.