Indeed interesting.

I could imagine that it is more likely to see hallusinations at old age.

"Why is that?" - Likely because you know exactly how your mom looked like. It would not be that hard to visualize someone you remember clearly in your brain.

For your brain to invent the image of someone out of thin air and hallusionate it to existense is a bigger task/harder.

- If I can dream about my dead mom, why would it be it much harder to hallusinate her as a ghost after her death?

- I could likely do it right here, right now. If I really wanted to hallusinate my mom. (I'am a super mental viszual person) but I won't attempt because it could lead to a permanent habbit/problem 😂