Or they complain that they know everything has gone to hell but if they blow the whistle revenge will be taken against them.
Everybody who worked with the 2005 Toyota Camry ETCS would have known what was up when it killed a few people, for example. Nobody can work on spaghetti code of that magnitude and not realize that something is off.
Boeing employees who tried to blow the whistle were similarly ignored or silenced while a few died in mysterious circumstances.
(The answer btw: Because nobody would be able to explain to a jury/judge that 80% or whatever is enough)