This is really underappreciated. I'm a big fan of diversification, and it can be very important to lower your risk-appetite if you're relying on your investment income in a short-medium timeframe (e.g. if you're planning on retiring in 5 years, being all-in equity is just silly, or if you're saving for a downpayment on a home in a few years, stock investing isn't the primary instrument to use), but in the long-term (e.g. a 25 year old thinking about early retirement someday) it just doesn't make sense to take too little risk.
And in part it's precisely because of the worst case scenario happens where worldwide stocks don't outperform treasury bonds, you're likely living in a world where your money isn't legal tender anymore anyway, and any stock/bond investment decision you ever made basically irrelevant.
So if decisions regarding the extreme downside risk are irrelevant, you might as well optimize for the upside.
Do note that there is a maximum amount of aggressiveness, beyond which you basically guarantee that you go broke while making trades with positive expected value. If you flip a coin that wins you twice as much as you lose, and you bet your entire bankroll, you'll eventually lose the coin flip and with it your entire savings.
For broad-market equity indexes, this point is at roughly 140% stocks / -40% cash. So it's not close to being an issue with current market expectations for a 100% equity portfolio, but generally speaking there is a level beyond which you cannot further optimize for upside at the expense of downside.
And in part it's precisely because of the worst case scenario happens where worldwide stocks don't outperform treasury bonds, you're likely living in a world where your money isn't legal tender anymore anyway, and any stock/bond investment decision you ever made basically irrelevant.
So if decisions regarding the extreme downside risk are irrelevant, you might as well optimize for the upside.