Sample size of 1, admittedly, but we’ve had life on earth for 4 billion years. We’ve had life capable of radio communications for about 50 years. That’s .0000000014% of the time life has existed. Maybe it wouldn’t be a bad assumption to think that only that proportion of stars would have even had the time to get to this stage.

Well, the building blocks of life are far from being life. It's like finding bricks and randomly a building appears. Sure, given enough time, samples, and agitation, it'll eventually happen. It's far from saying that if you find bricks you should expect to find buildings though. As far as we can tell, even on Earth, all life has come from one source (they all share common traits), yet we have even further developed building blocks for DNA and RNA. Hell, we have actual DNA and RNA floating about.

Maybe we're slow learners and aliens are better at hiding than us because they know better. Maybe Mars is teeming with life under the surface. Though, I guess we'd detect some pretty huge signals like methane exhausts and what not, unless they're just also very good at hiding that. Maybe Jupiter's gas is an artificial smoke screen. We could also be a lot physically closer than we think to dormant alien AI left over from long dead civilizations.