By doing that we are making a machine using natures technology.
It works, but we don't really understand how it works.
Maybe using machines we make ourselves, which self replicated, we could create planets ready for us to move onto. Complete with railways, houses, fields of crops etc.
All other things being equal in terms of space travel technology, it would be a zillion times easier to get a bunch of machine-based life-forms out to nearby solar systems than it would be to do the same thing with humans. And what's wrong with copying nature? If we didn't have natural examples to observe of things that can be done with the laws of physics, chemistry and biology that we have, we wouldn't know a dang thing about anything that's actually going on. Science wouldn't even exist.