@CathyJ30 Exactly this.
OP you don't know what people's previous experiences are, they may have had a relationship or several where they have felt really unhappy, therefore of course they are going to be careful who they let into their life. They may have experienced trauma. They may be scared to date or not feel up to it for whatever reason. Not everyone is full of SATC style confidence, and meeting potential partners everywhere that they are turning down.
I was way happier single than I was in my last LTR, and when you have been on your own for a while, it's a massive change to let someone into your life. Not everyone is surrounded by potential partners who live locally either, they may have to travel to find love and if you have health issues and constantly fatigued or have anxiety it may be difficult to actually physically go on dates with someone if they don't live nearby, also to put yourself in that situation with strangers from OLD may not even be safe.
When you are in your 30's & 40's you don't meet potential partners all the time like you do in your teens and 20's, and if you don't stick with someone you met back then it's hard. Just because people are single right now doesn't mean they have never had a relationship and why should they want to be with someone who is not even as good as their ex, who they are happier without? Or, they may have had a really good relationship and that's the bar. They don't want a relationship that's not as good as their last one. My Nan was widowed in her 40's, she never had another relationship as she said she had the best.
Not everyone is desperately searching for a relationship, if someone doesn't seem to be making much of an effort to find someone, they may be happy as they are...why give them a hard time over it? Or there may be medical problems that effect the sex drive or sex life in general, they may pretend to want a relationship because they don't want to explain to every nosey person who comes up and says "so....why do you think your single then?" with a big smug grin on their face like they are talking about the weather. They might be secretly gay or asexual, or they may be in the early stages of a relationship but not want to announce anything yet because they want to see where it's going and how they feel about it first, and they don't want the sticky beaks getting over exited and thinking they can finally buy their hat for the wedding. I think people that think like you do as in the "your too fussy" as their go to answer for if someone is single don't have any idea how insensitive they might be being.
I think the reason this subject bothers me so much is I had a "friend/colleague" who used to constantly grill me about why I was single and give me a hard time about it to the point of obsessiveness and would say things like "you'll never find the perfect man with no flaws". I was going through a bad time and it nearly pushed me over the edge as it was relentless. She would say things like "there's clearly a problem isn't there....you need to sort this out once and for all and I know you don't like me bringing it up, but as your friend I need to tell you it's not normal and people should be saying stuff to you". I no longer see this person.