I think the real reason so many of us believe in ET life is that the thought of earthlings being the only live thing in the universe is a terrifyingly shock-inducing, mind-numbing thought. Imagine if you will, a 5 year old boy (or girl. could be either) let loose in a huge mansion with uncountable rooms. For his own sanity, he has to believe that there are real, live people in other rooms in the mansion, even if he hasn’t come across them yet!