The definition of life matters because we want to be able to talk about extraterrestrial life as well.
The precise definition of life will not be the thing that will determine our opinion about possible extraterrestrial life when we come across it. It will matter whether that hypothetical life is capable of growth, change, producing offspring, heredity, communication, intelligence, etc. etc. - all of these things will matter a lot. Having a very specific subset of these enshrined as "the definition of life" will not matter. This is what Popper's quote is all about.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.