For something to be a store of value you want it to appreciate in value and have enough liquidity for you to cash out.
If you want it to appreciate in value there must be something driving the price. It cannot be others who only want to store their value as then the price is dependent on greater fools entering with new capital. Pure speculation cannot uphold the price long term.
Wanting Bitcoin to be only a store of value or only digital cash misses the point. It should be both.