At 20 my daughter decided that neither marriage nor motherhood were for her. She is a very direct and uncompromising person who needs a lot of down time. I suspect like most of the family she is neurally diverse, but the problem is less obvious than the dyspraxia and ADHD that afflicts the rest of us. She is now 50, has her own house, lots of friends, but can always retreat to her own home and be by herself.
I often think when people say they need a man in their life, that is because they are talking within conventional limits and what they are really saying is that they are gregarious and do not like living alone, so the thing to do is to look for ways of finding someone to live with you, a lodger, or a student, or a friend, male or female.
I confess that, despite having been happily married for over 50 years, I am very like my daughter. DH's work took him away from home a lot and it wasn't until he retired I realised how necessary to me were those absences. I still find never having much time on my own difficult to cope with.
So I would say, that having someone in their life to share life with is necessary for some people, optional for others, and to a smaller group, the last thing they want. Whether that person is the same sex, opposite sex, and whether it needs to include sexual relations is entirely optional.