Those few big companies probably have more than enough candidates. If you have too many candidates you need to adjust interview difficulty to still hire only as much as you need. I don't think these companies care that the task is too difficult for 99% of people, or that there are smart people who are not motivated enough to complete it as long as they can get as many smart and motivated people as they want.

That said, finding a job in IT if you are good at what you're doing is a dreamland currently, so declining if you think you won't enjoy working for a given company seems only natural.

Given dynamics above I think you're likely better off not working for one of those top few companies if you don't care about prestige and long term job stability.