Then you would have no motivation to be selective about what you upvote. Having a 'shortage' of votes means that something only gets a vote if you choose to spend one of your limited votes on it. Giving everyone enough votes to vote on everything they saw would probably result in every node getting lots of ++ (as people attempt to get xp for spending votes), and the differentiation between outstanding nodes and bad, indifferent or run of the mill nodes would be lost.