A vote for “none of the above” is a request for “someone else above”. The politician’s response is to try and be that “someone”. Here we come face-to-face with the problem of democracy: politicians must “do something” to attract votes.
An increase in votes for a party famous for offering to “shrink the size of the state” sends a (fairly) clear signal. Likewise, an increase of votes for a party offering “more public spending and investment in infrastructure” sends a (fairly) clear signal. Naturally the size of the increase – its value to potential governments – may or may not be worth a party changing its policies for: if it is they will, if it’s not they won’t.
An increase in voters spoiling their ballots, on the other hand, sends no clear message at all to politicians; it doesn’t matter why you spoilt your ballot, only that it is spoilt. You are not happy with what politicians are doing – this is obvious. What is not obvious is what the conscientious politician must do to appease you. But he must “do something”, and he will grope around in the dark, as it were, offering this and promising that, with no way to know when he should stop, desperately trying to “win back the trust of the electorate”. This hardly seems conducive to reducing the size and scope of government.