Scarcity only matters if there's demand.
I could take an A4 sheet and draw a triangle on it. It's scarce (there's only one A4 sheet with that precise badly-drawn triangle), but since nobody wants it, it's worth as much as the paper it was drawn on.
The same happens with both Bitcoin and gold. Since they are scarce, as long as there's enough demand their price will increase. However, there's a difference: gold has industrial uses for which there are no replacements with the same characteristics, and this provides a baseline level of demand. For Bitcoin, that is not the case; for any use case, there is (or can be created) another cryptocurrency which can be used instead of Bitcoin. This means there's no floor for the Bitcoin demand; for instance, if everyone decides that Ethereum's proof-of-stake is the best thing since sliced bread, the demand for Bitcoin can almost completely evaporate, and its price will go to zero. (There's a small intrinsic demand for Bitcoin as a collectible, since it was the first proof-of-work cryptocurrency, but that by itself is not enough to sustain its price.)