Because when you are sensing something your brain tries to find associations with past experiences in your memory and builds an "image" from that, and because p

Because when you are sensing something your brain tries to find associations with past experiences in your memory and builds an "image" from that, and because peoples have different experiences in their memories it becomes subjective and a little different for everybody. Also when it's something very different from your past experience the mix of the closest memories can be weird and seemingly unrelated.