When it comes to politics, a lot of people aren't looking to elect someone for their decision-making ability. They're looking to elect someone who is making the same decisions that they've made. For instance, people don't want a candidate who will "investigate whether universal healthcare is a good idea". The people have already decided whether or not it is, and they want someone who will agree with them.
In addition, not having a hardened position on something could mean that you intend to compromise with the opposition on that issue in order to appeal to more voters.