Your comment made something click for me: I just realised that I'm losing this ability somehow.
I'm in my late twenties, and as a teenager I was very into reading novels, very dreamy and would daydream constantly about things ( real-world situations, memories, or fantastic ideas).Nowadays I barely get into fiction, pretty much all I read is either technical or essays, and it's been a while since I have a memorable dream. My memory is horrible for personal events too.
I don't know whether this development of my personality is due of barely being able to see something in my mind, or the other way around - but I just tried, and realized that I can't do it anymore. I try to visualize a car, or a landscape, and I just can't, only abstract concepts come to my mind. I'm only getting flashes of an image when trying to "see" familiar faces, like those of my family.