Clearly, unless thinking beings inevitably wipe themselves out soon after developing technology, extraterrestrial intelligence could often be millions or billions of years in advance of us. We're the galaxy's noodling newbies.
Clearly, enriching the cosmos with heavy elements takes a while. So there's inevitably an interval between the sterile aftermath of the Big Bang and a time when the cosmic chemistry set had enough ingredients to make rocky planets (and squishy biology).
While I have always thought that the motivation for looking for E.T. was both self-evident and patently worthy, it's possible that I'm a victim of my own job description. Others don't inevitably agree. Some will opine that there are better ways to spend the money.