Space exploration is relatively cheap compared to our murder machines, and unlike the murder machines has practical benefits for a wide swath of people.

There's new innovations that come around in order to get into space, new innovations from discoveries made in space, and new innovations made because we've gone to space.

Some of these innovations even help address problems on our own planet. GPS helps keep planes from hitting each other (which was the catalyst for making high resolution GPS publicly available in the first place), satellite imagery aids in weather prediction and disaster response, even global communication is in part because of space travel.

I care less about finding backup worlds, but even that search gives us information about the needs of life and can hint at how life came to be--answers which may be helpful in some types of medical work.

Tardigrade can survive for a shockingly long time exposed to the harsh environments of space. We wouldn't have known that if we hadn't gone ourselves, and understanding why they can survive so long can help us look for ways to prolong resilience in other complex life forms and environments.

The knowledge gained about keeping people safe in space will be critical to keeping people safe in other extreme environments like through the ongoing climate catastrophe.

So for the sake of progress, yes, it's necessary. It's another frontier for humanity to explore, and the more we explore the more we find out about ourselves and how to help people.