So you can choose which one you like best, obviously! If I remember correctly, the default scheme on my machine was unbearable for me - it was too "bright".
"Owning" 10 colorschemes is useless. "Trying" 10 (or 20, or 40) colourschemes, though, may be a good idea. Once you have decided which one is your favorite what would be the point of keeping the rejected colorschemes around?