"Most burglars ... wear a mask, go to the back door between 11am and 3pm when most people are gone, kick it in, rummage for anything for 3 mins and then run away..."

Emphasis on the word "most" here. That implies a majority. If the author had said "some" or "many," that would be uncontroversial. Here, however, the author is making a specific quantitative/statistical claim, and it is that that deserves proof.