I have been harassed by airport security for the last 25 years. I don't remember one trip without some extra hassle.
I once asked a friend in the business for a possible reason and the only one he could come up with was that I might "look like a soldier". I am not and have not really been. About 90% of males of my age have gone through national service but that does not actually make one "a soldier" for the rest of his life.
I try to say as little as possible and answer questions but no help there.
And there are the idiocies like what is a computer, my small tablet apparently is but my large phone is not. They have the same capabilities and my phone actually has a larger battery.
They are there for the image not for actual security.