Look, there are a lot of possibilities out there in the "known" universe. The modern concept of scientists is to constantly ask "why" to things. To broaden the horizon of the mind, "why not" is far more statistically correct on just how big the cosmos are.


All in all, the modern layman may go an entire lifetime without approaching the thought of ET's beyond the human race. You, are one of the few that does, clearly.

Often, the concept of ET's on the planet is to think of a another alien race as mere 1,000's of years in advance when it is far more truthful to think of the possibility of another race as millions of years as advanced to the current type 0 civilization.