Blender will try to make the UV layout as a close match to your mesh, but it can only go so far depending on how you have seamed the model.Without being allowed to tear apart your mesh, Blender an only unpeel your plan and squash it flat like an orange peel… in order to prevent “humps” the flattened image is going to distort somewhat.
Your fingers are cyllindrical. If you simplify this thinking and make them something of a box… this would make each finger four times its normal width! (top, two sides and underneath). Each finger has this issue and they all want to spread out over the same space. Blender tries to even things out by shrinking them down to make room for each other.
If Blender makes your fingers skinnier, it will also try to make them shorter. Blender is trying to make the individual mesh squares maintain their shape as close as possible to your plan.
Not sure what you mean by “when i tried to move the UVs to match the image” as this could be a number of things… perhaps a screenshot to clarify?