These types of techniques serve to help us break out of boxes we built for ourselves. Breaking out often inspires a new level of creativity, and even occasionally, insight. These represent the evolution of skill, in that once you understand a "rule" and can make images that conform perfectly to the "rule", you can now set it aside when the artistic need arises.
The human brain is very visually oriented, and we also seek out patterns in what we observe around us. These patterns can be visual, auditory, tactile, temporal, or some combination thereof, but we tend to "connect the dots" and see patterns where none exist. We also like stories and depictions of cause-effect (partly because these serve to create a sense of order, and depending on your political/religious persuation, a sense of purpose).
These techniques cause the viewer to have several reactions:
1) What is this? (recognition)
2) New! Shiny! (novelty)
3) How did this get done? (what's the trick?)
4) What does this remind me of? (association/feeling)
and occasionally
5) How does this help me understand or see? (perspective change/paradyme shift - rare, but powerful when it happens).
I think all of us, as photographers, should have a list of deliberate rule breakers that allow us freedom to explore and try things we've never done before. Most of the time, the end-result won't work. But when it does, it will be because there is a pattern that the viewer can't immediately recognize and explain, and that forces a much closer examination. When the item is ambiguous, the viewer then injects their own interpretation (because we are seeking patterns, causes and effects, a sense of order), and in doing so, may open (inadvertently) the doors to (new) perception.
My way of thinking of it is that a picture that is "complete" can be viewed, but is rarely experienced, but a picture that is "open" or "unfinished" invites the viewer to add their own ending, so to speak, and in doing so, involve them emotionally. As a photographer/artist, I find creating such "open" images to be very difficult - partly because there is such a great temptation to get to the punch-line, or tell the end of the story.