"Make younger workers pay more because..."
...because their longevity isn't properly worked into the equation yet. Folks entering the workforce today will average into their 90s. Kids born today will live nearer to 100.
Until/unless the "adults" eff it up, obviously.
BTW: the reason life expectancy has decreased recently are due to two historical blips: the opioid crisis, which killed fewer, but younger, cutting an average of ~30 years off expectancy, and Covid, which killed more, but leaned toward the obese and the elderly, cutting an average of ~2-5 years off expectancy.
If we don't have another bout with waves of Covid, expect headlines over the next 3-5 years to crow about leaps in American longevity.