But, this means that the low risk investors are susceptible to just as much bet size variance.
Yes, because bets vary in size...
Forcing the 1% investors to take all the variance so the 0.25% investors don't have to isn't fair on the 1% investors.
Investing at 0.25% allows you to risk less of your investment per roll. It doesn't change the fact that most bets aren't near the maximum. It allows you to select your own risk of ruin as you see fit.