i heard that dreams that happen just before you wake up are the result of stress. it dosnt really make sense, but im not a psycologist, so who cares what i think.
I was reading that you dream all night short dreams. I can’t recall the specific intervals. It is possible that you are dreaming happy dreams all night and would not remember even your last one had you not been rudely awakened. On the other hand maybe it’s so you can wake up and live it! : )