Life ... now that's the game-changing question. Is the interstellar space in our galaxy actually full of life? Possibly. From what we know of other planets, we have to assume that nomad planets will share some similarities. And from what we've discovered so far, we know that most planets couldn't support life as we know it. But the law of averages on a galactic scale says that life can exist. We're living proof of that.
Even Louis Strigari, the leader of the team behind the 100,000 nomad-planet-per-star-estimate, said this to Stanford News: "If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist." In this case, some rare planets could harbor life forms that have adapted to live in the most extreme conditions in our galaxy.
Likewise, some nomad planets might be carrying the remnants -- or building blocks, depending on which way you choose to view it -- of life in their previous solar systems. Given enough random encounters with asteroids and other debris, they could be spreading that material across the galaxy.
Finally, it's entirely plausible that humans could inhabit a nomad planet one day in the future. Proxima Centauri, the closest star to our sun, is a considerable 4.22 light-years away from Earth. Nomad planets could become the space bases of human space travel. Once we break out of our solar system, we could use hospitable nomad planets to island-hop our way across to another star system. Then again, with so many planets out there, we might not even need to go all the way to another star to explore new ones. That big, empty blackness between the sun and the stars is suddenly full of potential -- and questions to be answered.