Yet another clickbait headline. From a Harvard professor, no less, assuming the title is the author's.
The article explores the consequences of our reluctance to break from habit, rather than explaining why we find this hard to do.
More accurately, it explores why we so rarely do it. If we were discussing it being truly 'hard to do', we'd need to first establish that we consciously want to break from habit, but then fail to follow through with action. The article doesn't take this route.
The closest it gets to delivering on the title is Yet the fact that many people needed a strike to force them to experiment reveals the deep roots of a common reluctance to experiment. This is not then expanded upon.