Why can't we find any signs of extraterrestrial life?

For over 60 years, amateur and professional astronomers from the SETI project - "Search for Extra-Terrestrial Intelligence" - have been observing the skies in search of dʹintelligence extraterrestrestre, but without conclusive results. How do we interpret this silence? Are we missing signals because our detectors are not sensitive enough? Are our radio telescopes pointed in the wrong direction? Is there simply no extraterrestrial life in our galaxy?