We forget dreams to forget nightmares

An idea came to me while I was waking up.
I think there are two possible points of view on vanishing dreams. First is that bad dream recall is a side effect of some fundamental process in brain. And the second is that bad dream memory is nesessary by itself and it could be naturaly selected.
And I think that bad dream recall protects us from recalling bad dreams. The nature is blind and it doesn't distingwish between good and bad dreams. But the individual does. And the ability to recall bad dreams clearly may influence bad when waking up. So it is better to remember nothing.
For me this is the simplest explanation.
But i don't know how to verify it.

What do you think?

It is a nice idea.
My personal experience points to memory being tightly related to significance...

Things with perceived significance are remembered. This would imply that as soon as we start caring about dreams and viewing them as significant and interesting we should also start remembering them. Not true.
The reason is that significance in this case has to be seen as a behaviour pattern. If we actually behave as if the dreams have significance(dream journalling etc.) recall will increase. I think this is a very good theory.

As for why we don't remember dreams from earlier in the night is probably, among other things, related to a lack of a continuous narrative.

Another important thing to keep in mind is this: It is easier to find a memory if it is similar in nature to the experience you are having when trying to recall. Great differences in state of mind and situation between the time of memory creation and recall creates difficulty remembering, up to the point of recall being practically impossible. Applied to dreams: a dream that is very different from real life is very difficult to recall in real life. But could possibly be recalled if you are ever in a similar dream.

Interestingly enough this implies the possibillity of continuous narratives taking place every night that you can not remember as they are to alien. You could spend a day being a butterfly every single night and not remember it in human life if the experience is different enough from being human.