A lack of theory of mind.
My MIL, although I am quite fond of her, is the classic example. She had a tough early life (eldest of 13 children, mother continually pregnant or miscarrying, parenting the younger ones, in a household that didn't value girls), and I think it wasn't an environment that was at all conducive to developing an imagination, or indeed any conception that other kinds of lives were possible.
She's in her early 80s now (but she was in her late 50s when I first knew her, and was always the same) and is never going to change. She gives everyone the same advice, all the time, regardless of their circumstances, and repeats it until they give the response she's looking for.
She will do exactly the same thing every time, and proclaim its effectiveness, even when the evidence is in front of her that it's not -- a tiny example, but with literally every baby she comes into contact with, including her own 14 grandchildren and great-grandchildren, she will click her fingers repeatedly an inch from the babies' eyes, and when they (almost inevitably) get irritated and cry, she looks annoys and says 'They love that, babies'.
She has a similar thing that she does with toddlers, where she takes a toy away from them and dangles it out of their reach, and when they cry, she says 'They love that'. It's as though she only has a certain set of entrenched ideas about behaviour and responses, and will cling to them no matter that the evidence of her own senses shows that it doesn't produce the desired effect!