Why yes, you are missing something. The vast majority of bike thefts are crimes of opportunity (ie unlock or not properly locked bike) or bikes locked with cables, low-end U-locks, or low-end chains. Thefts using power tools to cut through high-end locks are quite rare for several reasons. The first being that most thieves are junkies, so they would have sold their power tools long ago, and the second being that there are plenty of nice bikes locked up with low end locks that can be defeated with almost no effort and without the need to buy new cutting discs every day.