i have seen many things i couldn't explain like a triangle of lights passing over me at low speed with no sound. but i am not going to jump out and say it is aliens. instead i just didn't know what it was.
anyway people also have a tendancy of making up stories to make themselves feel better. as such we try to define what we don't know. the saying that ufo=aliens is one such definition. we might be scared of aliens we are even more scared of the unknown so we pick the lesser of two evils.
now as to the idea of whether aliens exist or not all i have to say is if there is no other life in the galaxy there is a lot of wasted space. :-)
