Because gold will appreciate reliably to an extent but a company can appreciate in value far exceeding what gold can -- that's the risk/reward trade off.
The chances of a startup failing is way higher than gold degrading in price.
It sure is and many do choose gold for this reason. It depends on how much risk you want to expose yourself to.
Hence why the potential upset of a business is so much higher. Risk vs. reward, as usual.
if an investor already has X% amount of their portfolio invested in gold, they might seek to diversify by investing in uncorrelated ventured such as startups. an investments idiosyncratic risk/reward is only meaningful in relation to other investments in the universe of choices the investor can make.