Your reasoning here is tainted by survivorship bias.
Yes, founders and employees share similar levels of risk in a startup that has reached the point where it can hire FT employees.
But before the startup hit that point, it endured a period of drastically higher risk, which the employees never saw, and which the founders are being compensated for.
The only conditions that must be true in my reasoning is that (1) an early non-founding employee faces substantially higher risk than a corporate job, (2) at lower pay and with substantially less equity than would compensate for that risk.
That the risk was higher for the founders prior to the FTE is certainly true, but irrelevant, because we are not comparing whether an FTE has a good risk/reward tradeoff relative to an opportunity to join earlier in the startup under the same terms, but rather relative to a corporate job.
Yes, founders and employees share similar levels of risk in a startup that has reached the point where it can hire FT employees.
But before the startup hit that point, it endured a period of drastically higher risk, which the employees never saw, and which the founders are being compensated for.