Every Social Security rule I can think of is gender-neutral. In other words, the same laws apply to men and women equally. But society hasn’t always been gender-neutral. We’ve all heard the statistics: Men tend to make more money than women. And because Social Security benefits are based on lifetime income, men end up getting higher Social Security benefits than women do.
Also, biology isn’t gender-neutral. Women have babies. Men don’t. So women take more time off work to have and, frequently, raise children. That’s just another reason women end up with a lower lifetime income and, therefore, less Social Security benefits than men.