Older man dating a younger woman is still culturally accepted but not vice versa. Statistically, this means that the dating pool for older men just keeps increasing.

For older women, the situation is the exact opposite. Their dating pool, which consists of (say) all older men keeps decreasing with age.

That might explain why your older female friends find relationships harder as they age, rather than a decrease in their physical attractiveness. The latter is what many women attribute their situation to, but IMO its just statistics and preferences.

That's true.

But what's also true is women tend to want to settle down in their early-mid 30s (at least in large American cities, among professional types) and now they become simultaneously more selective. In a sense, women are always the 'choosers' with rare exceptions. Men tend to have wider nets, on average.

That sounds like they were never interested in romance or relationship (beyond it being the means to get sex).

Looks like the latter's convenience might explain the former's predicament.