Generally, the people who are in shelters are those who are younger, partially because accepting a family into a violence against women shelter is often the priority. The most extreme forms of violence are often experienced by younger women.
Also, there are existing policies that make it very hard for single women, and older women are generally single. They make it very hard for an older woman to find a space in a shelter. There are very limited spaces for older women in shelters. Not to mention that communal living for an older woman is also a very hard situation for her to be in after she's been living by herself and has been autonomous for a very long time.