They are aware of the possibility of alien life, it's just our ability to view said life is extremely limited. Given the amount of planets in our current solar system/galaxy that provide the correct resources to host life are extremely low. There are still probably 73 million planets that can host human/ alien life but our scientist can only view 3-4. One of those planets was only found just recently. Not to mention the closest planet that has the ability to host life is so far away that our telescopes are viewing it millions of years in that planets past. As we do not have a device that can view these planets in there current time. Just as if you were on one of these planets with a telescope powerful enough to view earth, you would see any movement because you're viewing Earth 12 million years ago. One of the reasons we know this is because of when we were trying to measure the speed of light by shining a lazer down a pipe. You'd need one clock at the beginning of the pipe to tell when light entered the tunnel and a clock at the end of the pipe in sync with the clock at the beginning to stop when the light passes through the senor to measure the time. Their first idea was to have both of the clocks at the beginning and when the first clock starts the second clock rides along a rail system to the end of the pipe to catch the light with it's sensor to stop the timer. Their issues were that the clock on a rail wouldn't be able to keep up with the light and even if it could although the clocks were synced at the start of the pipe, when the clock on a rail would reach the end of the the pipe, the clocks wouldn't be in sync anymore. This observation of time multiplied by the distance between planets make it extremely hard to view other planets in their current time zone making it more complicated to view alien life.