I don't know exactly, but I would guess it's because you have to pay for skins, and so we wouldn't able to get a good screenshot w/o having to 1. Use up a lot of our gems or 2. Pay for gems to buy skins. Lots of us are F2P. As for star point skins, we simply don't have enough star points. The total cost for just Brock's skins is 460 gems. Total cost for Bo's skins is 60000 Star Points and 150 Gems. That's quite expensive for just 2 brawlers. Think about it.