What I'm saying is that the biggest ISPs do not compete with each other and tend to stay out of each other's territory.
Indeed, where the requirement to 'steal' a competitor's customers is that you must install new infrastructure (run a cable to each premises), while your competitor has already got that cable in place, it is near impossible to be competitive.
Householders won't pay for a second water supply pipe, a second electricity cable, a second sewer connection or a second Internet cable to be connected - because it is invariably cheaper to use the one they already paid for. Such infrastructure forms natural monopolies. Expecting competition in this area is crazy, and only rabid free-market ideologues with no grasp of reality would suggest otherwise.