"Real" prices are almost always measured in CPI terms, although sometimes the GDP deflator is used (it was CPI in that chart).
The real value of gold was (relatively) flat until gold convertibility ended in 1971 because the price was being fixed by the western powers under Bretton-Woods. Ever after it's been on a non-stop roller-coaster ride. If you bought gold in 1980, far from its value being "stored" it would have lost half its value in 10 years even if you bought after the spike.
It sounds like you don't value low CPI volatility very much (perhaps CPI goods and services are of little interest to you), which is fine, but many would use CPI volatility as the definition of a "store of value" as opposed to a speculative investment.
> When measured in dollars
No, when measured in real terms.
> which have lost 98% of their value since 1913.
Nobody would suggest that dollars are a useful store of value. They are a useful medium of exchange and in the short term, a useful unit of account.
