I've used cash a fair bit in the past year, for a few reasons. I know some food places prefer it (I ask even if I don't see a surcharge, since I have it on me anyway), one otherwise-normal shop I know simply doesn't accept card payments at all (has an ATM in the store), I know a tradie or two who offer cash-in-hand jobs in the future to bypass their regular employer's large cut, and sometimes I simply don't like banks knowing my spending habits and potentially running analytics on them.
I am surprised to see a non-trivial chunk of 18-29, compared to later age demographics, using all cash.