The rationale behind 261 was to dis-incent airlines from overbooking flights inordinately and inconveniencing passengers without adequate compensation.
The "they cancel flights due to low loads" is a red-herring. Might have been the case before advanced network planning when an aircraft and crew did A-B-A-B-A all day, but the network impact of a cancellation in today's environment is severe, to say the least. As a previous poster wrote, the difference in cancellation levels pre- and post-261 is static.
I assume that we all understand the concept of MTBF/MTTR and we all accept that complex systems are unlikely to operate unimpaired until obsolescence.
So do we expect a manufacturer to compensate us if an out-of-warranty vehicle refuses to start? Do we expect the same for a refrigerator manufacturer and do we SERIOUSLY expect consequential damages for spoiled food?
I do wish that people would put on their Captain Sensible caps and accept that a) we live with risk b) there's not always blame to be apportioned and c) "life is a box of chocolates; you never know what you are going to get."
By all means compensate Denied Boardings, but don't seriously tell me that bird strike should be compensatable "for the simple reason that our skies are populated with birds" (a judge at Manchester County Court)