Why is the most obvious solution overlooked?

Quite simply, male life expectancy is approximately 81 years, and female life expectancy is approximately 84 years. If males are expected to retire at age 67 and have 14 years post-work, then for equity women should retire at age 70 and also look forward to 14 years post-retirement.

Those extra 3 years of contributions will compensate for time that they have taken off earlier.

In most cases, women currently retire around the same time as a (typically) older male partner, meaning that they already aren't working until the same age. Obviously this shorter investment timeframe is also a significant factor in why they may not have earned as much in their super.