Actually, it's a good way practicing how to restore those as well. There's less at stake with already extinct species. We've wiped out plenty of species already and we probably have a growing amount of DNA to play with. I take it as a given that there will be a lot more species disappearing over the next decades. So, any early successes with this will be helpful. Once we clean up the planet in a few centuries, we'll be able to restore ecosystems this way potentially. A key thing for that is figuring out how to get genetic diversity to avoid inbreeding becoming a thing.