Several factors work against detecting extraterrestrial radio transmissions.
One is it requires a tool-building species. There may be many alien species with high intelligence on other planets, but if they're not tool-builders, we'll never detect them. Think of a species like whales. Apparently quite intelligent. They even have music. But with those little flippers they have it makes it difficult to build anything.
Another factor is radio transmissions simply are not powerful enough and they get scattered and absorbed over interstellar distances.
The third factor is the narrow time-band where a civilization may actually use radio transmission. On Earth, we've been using radio transmission for about a century, a tiny fraction of time on a cosmic scale. Other alien races may have ascended, declined, and extinguished themselves millions of years before.
It is rather cool to speculate on however small the chance, of picking up the alien equivalent of "I Love Lucy" from some alien world.