> What are we trying to find or learn that life from earth will permanently remove the chance of?

Species prove to be invasive all the time on earth when exposed to new ecosystems or environments, and usually that's at the expense of many potential discoveries about the life forms that are replaced.

Seeding the universe with life from our planet may make sense as a survival strategy, but there's no ceiling to the knowledge we can glean from life thats different from our own.

In short: we don't know what we don't know, and the gains from such knowledge could be endless.