There are several things here.
One is that you're only considering direct monetary risk. For example, imagine a person that starts a business with X dollars, which will usually be a percentage of their wealth. This person hires an employee at a salary that's barely above their living expenses, but with the idea to ascend as the company grows. If the company goes bust, who loses more? The owner still has money, the person living paycheck to paycheck might not have enough funds to live until they find a new job and they have probably lost money because they didn't go for a higher paying job (with less upside but more safety).
Two, the risk/benefit ratio is not fairly distributed either. If I have a hundred dollars in the bank I cannot really access any investment opportunity, like creating a business, that could multiply that money with the same risk.
Three, thinking only in relative terms is a mistake, even if risk/benefit ratios were evenly distributed, because not all people have the same relative expenses. For example, assume both person A and B get into a stock that after a year gives them a 50% profit. Person A invests their emergency fund, which is $1000 bucks. Person B is far more wealthy and invests $100k, and they still have a lot of money leftover. Here, A is actually taking on more risk because losing that thousand dollars means they might not have enough money to fix their car or pay for health treatment. Person B, if they lose that money, it will hurt but it won't really change their living situation. And when the profits come, A has $500 more, which is not that much and probably goes into the emergency fund again; but B has earned $50k and probably has enough to go on a super nice vacation and still have a lot leftover. In other words, even if the risk/benefit ratio is the same, the actual consequences are not equal. Having more money makes the same ratios far more beneficial in practice.