The response I am gonna give whenever I am asked why not married yet from now one. And it's the absolute non-PC brutal response truth.
The response would be:
"Well, because I am generally unattractive to most, I failed to attract enough potentials, so I simply failed to make it happen; and that's ok; it's ok to admit of failing in some area in life and to live with it".
I expect their reaction to that would be something "But but...bla bla bla <some lecture about how to be confident> ".
I would explain further: "It happens all the time everywhere, in humans, in animals, in nature, for example plain colored male birds or bad singer birds for example often fail to attract a mate, because they don't have the required set of characteristics/skills to make it happen, they're not a mate material - some humans are like that too, I am in the same status of those and that's ok and I am totally ok about this reality, I hold no grudge against anyone."
What do you think? I mean I am sick of giving cliché responses like "Didn't find the right person yet" or "still seeking for Mrs. Right". Like come on, such white lies are believable when you're in 20s or early 30s; they are no longer believable once you are in 40s. After a certain age, It becomes apparent that the main reason is the single person in question him/herself so why denying.
That response would shock the recipient(s) as It would not be expected, but it will shut them up for good regarding this topic, it would be a closed case.