Not voting can mean that no-one is putting forward a policy (or in the case of most elections in this country) set of policies that you support. If, for example, I like one party's policies less than than another's does that mean I must vote for the ones I dislike less? In my case that would be quite hard as I often struggle to decide which is worse. I am happy to have a discussion with anyone about what I think, I'm not prepared to endorse a whole swath of policies I disagree with which is what voting amounts to imho.