They're "different". Also, easier to mine. I personally don't see the point, unless you're the guy who invents it, and secures the first million coins or so for yourself.
It's just greedy versions of Satoshi who don't actually invent anything.
I would agree with this as it relates to most alt coins, but some definitely have their uses. Alt coins will rise and fall, the market will decide what's useful and what's not.