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.
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.
There are other good replies as well, but I would add to the list mission-based investing.
I would easily consider a positive impact along with risk and returns when making an investment decision. Not everyone would, and not everyone should, but it is a part of the funding landscape.
10M to 20M in what amount of time? This is not incidental, it is critical to determining IRR (Internal Rate of Return).
If the company goes to 20M in 10 years, that sounds great, but is only a 7% compound rate of growth. I can get that with much less risk by investing in the S&P 500. And don’t discount the risk. It is critical. A small business has a very large chance of 100% total loss. Compare that to the 500 index, which has a very small chance of a 50% loss, max.
To count for risk, I would look for a doubling (10M to 20M) in at least 2-3 years, min.
You also have to think about liquidity. If you want to cash out, who is going to buy your shares at the price you want? This might not be as easy as you might think. I can liquidate 500 index shares in seconds. It might take a year or more to find a buyer for your 10% at the price you want.
It sounds good for me as a founder, but from investor point of view, this is pointless. Why taking a huge risk for 10%?