Again, I'm amazed that you're on the space subreddit. Habitable planets? Is that the only purpose for innovating in any form of space age technology? It is most definitely an epic failure of imagination to assume (as you said, "all that is left") that space has no other practical purpose or benefit. I'm not even going to start listing them. If you don't have an idea what they could be, it won't even make sense to you.

I run a design and engineering firm, I am an investor, and sit on an incubator board to provide funding to new medtech startups. I've bet on many, many companies over the years, and only a few make it, but I've learned two things in the last 35 years. One: Failure and improvement can lead to riches, and Two: I've always failed to predict where tech goes, but it has always been better than what I anticipated.