She may be active in her community as well, and may be devoting time every day to keeping herself physically fit and youthful.
As her children get older, she may expect to become more involved in her community, have additional time to develop her profession, or start a new career.
A more significant reason is that relationships that lead to marriage are built upon compatible expectations and goals, but when a generation divides a couple, their expectations and goals seldom match.
They may have similar worldviews and may both want children, but that's where the similarity ends.
In our experience, the larger the age gap, the more "spectacular" the man's credentials need to be for her to consider meeting him.