In the case of religion and politics, it seems more difficult to maintain a lack of strongly-held opinion, as attempting to do so puts you at odds with most people who have one. Inevitably, someone will try to argue that your faithlessness or lack of political conviction is itself a faith or conviction, and it may very well become one if you get pulled into that.

Meanwhile, the even the most free-thinking of the faithful in anything come equipped with dogma, which requires little mental energy to invoke. This partially explains why arguments tend to be the same over and over again--they've been reduced to dogma vs. dogma.