Going to the shop and buying stuff does not proove that its a...

Going to the shop and buying stuff does not proove that its a store of value, this proves that it is acceptable as a form of currency.
Every day of every year if you have cash, you ARE loosing purchasing power, this is the exact opposite definition of a store of value, going back to the lollie shop example, if I had the same value in gold 20 years ago, I could still buy the same amount of goods today, that is a store of value. One of the costs of convienence for cash / currency is the fact that it looses its purchasing power, i.e. not a store of value.