Reason being is that I can see a fair bit of empty space (the black space) around the islands in your texture image – which leads me to think they’re too small.
When unpacking UV’s you want to take up as much space as possible, while considering the which islands needs to be bigger and which others can be smaller. There are tools and addons which can optimise this for you, but of course it always helps to go in and do necessary touch ups!
