If I put 100% of my investment into a single coin would be sweating bullets all day long.
Then bitcoin or litecoin would go up to some crazy, never imagined before height while proto's went under, or vice versa - and my suicide would be so spectacular it might make front page news.
But this way if I "lose money" by spreading my investment out so that 1 outperforms the other I can just write it off to being cautious and having a balanced portfolio. Also helps justify wasting more time cruising the various forums.