It's probably to make them look more aggressive =P and apparently it helps in case you're about to be attacked or going to attack lol. The outsiders also seem to have longer, sharper claws than the Pridelanders, probably to be like Scar- y'know, sharpening his claws every day xD
My graphics thread And where the journey may lead you Let this prayer be your guide Though it may take you so far away Always remember your pride
I think they have their claws out because they're more aggressive and the fact that they're evil. ^^ I kinda have a sense they like to display their dominance or show warning towards the other lions. ^^
I think Disney just wanted to make it clear that the villains are evil. By showing them with claws out all the time, it looks like they are always about to slash you.
It's probably a hereditary thing. Most of the Outlanders have their claws unsheathed most of the time but the Pridelanders don't. Just like their noses.