@SapphireSeptember
I get you OP. I am now in my mid 50s, and I didn't 'find a man' til I was in my mid 20s. I was single - I mean never had a 'steady boyfriend' - til I was in my mid 20s. I had a few 'encounters' and a few men who I met 4 or 5 times, but it never went past that. I was 20 before I lost my virginity!
People asked my mom if I was a lesbian, well-meaning friends and colleagues tried to 'fix me up,' and older/elderly neighbours of my parents used to ask me 'are you courting?'
It was like a woman is not complete without a man - and kids obviously.
It was the early 1990s, and I lived alone in my own flat, and was 'pitied' by everyone. Yes I got the same 'you'll find someone one day' and 'why is a pretty girl like you single?' comments all the time. And the fact my 4 female cousins were all hitched by 21 (and had their first baby within a year,) didn't help! I was the odd one out, and the one who was pitied. The number of head-tilts I got really fucked me off! 
Then I met DH, and people were soooooo pleased for me, and clapped their hands with 'joy' when they saw me with a MAN. 
Anyway, we got married at 29, and had our 2 kids before our mid 30s... I do love him, and adore my kids, and me and DH have had a pretty decent marriage (not without its flaws and hurdles, but more pluses than minuses IYSWIM.) We do a lot of things together and enjoy each others company, but do stuff apart too (with our own friends.)
I certainly don't see single middle aged (or younger) women as a threat; indeed, the 2 women over the last few years who HAVE made a play for my DH have been married. Same with me, the 2 men that made it clear they are up for an affair with me, were married too! So it's not just singles who are a 'threat.'
I actually do enjoy being married, and the companionship etc, but I do have times when I think it would be nice to be alone, have meals when I want, just have sandwiches or soup for dinner instead of having to cook every evening. Also being able to just lie in on Christmas day instead of getting up sorting Christmas dinner, (and 'doing Christmas' and having to visit relatives,) and being able to watch anything and everything on TV when I want to watch it, instead of recording it and waiting til DH is in bed or at work! We do watch some stuff together, but I have stuff only I watch...I work 3 days a week and he works 5, so I get time then. 
It was also quite hard work raising kids, with all the trials and tribulations involved, school-gate mafia, school politics, awful 3 or 4 years during their teens, siblings scrapping, trailing around loads of universities, all the extra costs and so on... But like my marriage, there were more good times than bad.. 
I have to say, if I could go back 30 years, I would not change a thing. I do love my 'me-time' but I also love doing things as a couple, and I have enjoyed soooo many family occasions. I have had some wonderful times with my kids. (and my DH.)
And although I have had phases where I envy single women for the reasons I listed above (not having to think of or consider someone else when you do anything,) I wouldn't switch places with a single woman. I have to say that the single women I know (who never married or had kids,) are amongst the loneliest people I know now. Especially the ones middle aged or older.
I'm not saying it's a given, that a perma-single woman will be lonely in their 'middle age and older' years, or that married women are eternally happy, but I do know a few 'never-married' women over 45, who never had kids, who live alone, and they seem to crave companionship. They are out all the time, doing evening classes, taking part in various hobby groups, and trying to rally people around into community activities. It's like they are desperately trying to forge a social life to get themselves out of the house.......
Most people can't be bothered because they're happy to sit in front of the TV or go out to the local boozer with their other half. The older single women do seem rather lonely. And I have to say, I don't envy them, spending their older years (45+) alone, with no partner and no children or grandchildren etc... Indeed, I do know half a dozen women like this, and a couple of them (48 and 51 y.o.,) have admitted that they are excruciatingly lonely, and dreading their 'pension years' alone.......
As I said, for all the trials and tribulations of being a wife and mother, I would not swap it for the world. The positives outweigh the negatives massively. I love my husband, we are soulmates and great buddies, and I love and adore my kids, (now in their 20s,) who are now also friends of mine and DH's (as well as our children.) We have had so many good times, and I have done so many things that I would never have done if I hadn't had children.
So although society DOES make women feel like they should be in a relationship, I have to say it may be because most people are happier in a couple. Not because 'society says so' but because it's just nice to have a companion in life. It can get very lonely being alone long-term. Even when I was single in my late teens and early 20s, I got lonely, and disliked being single. I am much happier in a couple.