Egocentric bias.

Imagine instead you're an ant living in an ant-hill in the middle of the Amazon feelling around with your feelers, wondering why you haven't seen any any other type of intelligent life capable of building such awesome ant-hills. Our problem as a species is, we intrinsically think we must be special enough that any other species should want to travel to our specific anthill and/or communicate with us if they had the ability to --rather than generally ignore us as uninteresting as we humans would an anthill. We used to think the Earth was the center of the universe. Now we wonder why aliens don't communicate across the light-years in a way we can detect with our primitive ant-feelers.

That said, it does appear we may have detected repeated energy bursts in the range that would be ideal to push solar sails between solar systems.