I think what would explain this is our very limited timespan when we started listening to universe. There might have been 10 strong signals in last 2000 years,

I think what would explain this is our very limited timespan when we started listening to universe. There might have been 10 strong signals in last 2000 years, but last one could have happened around the time US declared independence. And 2000 years is nothing timewise on scale of universe. Plus we talk about signal that can maybe travel few hundred / a thousand light years before they blend into galactic and intergalactic noise.