Skins are used to replace the original textures of a model with new ones. I think that what you're trying to say is that skins look useless, but they aren't. Sometimes, when you want to make a big map that you need all the original models, you may have difficulty using the skins as you can't use the old model's textures. Althrough if you are making a map like fel orcs against Humans, you can use (for example) Afro's skin of a fel keeper etc. You may realise that skins can be very usefull, since they don't take so much space on your map. An example is: Your making a DotA map of Fel Orcs vs Humans (like I said before) and you want a fel keeper. Instead of using a model that will take like 30-60KB for the model/portrait and 40-90 for the textures for that model, you can simply import new textures for the already existing model, which saves up much space.
Skins are used to cover up an entire model, regardless it's a skins from blizzard or custom skins made by another person. Without skin, you can't use a model (.mdx), it just displays a bunch of polygons on model editor.
im pretty sure this hasnt been covered yet... what are they used for??
Unfortunately it had been covered since "what models are for" covered.
.. just changing the colour of a model doesnt do anything....
Right, skins which just changing color (merely) doesn't do anything. But, a great skins doesn't just change the color.
lom109im pretty sure this hasnt been covered yet... what are they used for??.. just changing the colour of a model doesnt do anything....
changing the color of the model is a recolor, which arent encouraged here. skins may not seem much, but they make all the difference. a model without a skin (or a good skin) would look dull, boring, undefined, and just plain crappy.