A lot of times you create a model in one application and rig it there or let it rig by someone else.
You can only export fbx there. But you need dae. So you convert to DAE A. But your skelleton B does not match the skelleton C you need in your other application E.
So you load a file D that is working with E and which contains C, you remove the mesh of C, apply C to the mesh of A.
You run into tedious work, the skelleton needs to be aligned and weighted.
Is there a software you can give a DAE/PMD/FBX/some-3d-format-with-bones with skelleton X which automatically converts the file to DAE/PMD/FBX/some-3d-format-with-bones with skelleton Y, ie automatically guesses which parts are legs and arms and so on and also converts.