I’m not sure all ancaps would agree they are a political movement. Many would say they are antipolitical because their wish is to do away with the state, not co-opt its power. Maybe this is splitting hairs; regardless, the purpose is to do away with the state or make it irrelevant to yourself or your community, not necessarily through voting. 

Attempting to get votes is meaningless if you don’t actually change a local critical mass of hearts and minds. 
All efforts to remove a structure like the state fail if there aren’t parallel systems. 
Most ancaps I know focus more on these two strategies, anyway, whether or not they touch political means. 
Ones like me only see parties and politics as useful insofar as they get ideas in front of large amounts of people who are listening, like during election seasons. There’s no actual expectation that there will be enough votes to win an election, only that someone will hear and think.