There could be several reasons why an older unmarried woman is still single. Perhaps she wants to complete her education and get settled in her career. Perhaps she was in a failed relationship and would prefer to get over that before committing to someone else in the future. Perhaps there are difficult family circumstances that are hindering a marriage. Perhaps she's just not in the marriage-frame of mind. Perhaps she wants to take the time out to know who she is. Perhaps she doesn't want to just settle for someone that her heart is not into and she's not sure about. Perhaps she'd rather wait until she meets the right person and is ready.
It's wrong to assume that ALL these women must hate the feeling of being single simply because one has encountered a few that do hate the feeling. It's wrong to assume that ALL of them must be sad......and some of them might be. Some of them might be confident throughout the day......and then when they detect the pity from others......it's natural for them to feel uncomfortable.
It's better to first request/find out all the reasons for why many women are single.......before deciding to feel sorry/bad for the whole female singleton group.