For one thing, it would provide scientific data on how Earth-life adapts to alien environments. Who know what it might evolve into. If life has not evolved on Europa after 4 billion years, I doubt it is going to start now.

In a universe where life-less worlds probably greatly outnumber those with life, I see nothing wrong with spreading life around. Most of this universe’s matter is lifeless. Even here on Earth, the majority of matter is not contained within life.

Ponder this- how much of this universe’s matter is actually part of self aware creatures. I think, if we had the data, we would find it would be a minute amount (Even if we considered all of an intelligent being and not just their brain.)