Most companies like to think that they don't have any "bad" projects; if they did, they would cancel them. And, they're afraid that employees will confuse "hard" projects with "bad" projects, and try to flee the hard projects, which are often business-critical.
Google is smart enough to realize that employees can often identify bad (and good) projects before the management does, and lets them vote with their feet.
Most companies like to think that they don't have any "bad" projects; if they did, they would cancel them. And, they're afraid that employees will confuse "hard" projects with "bad" projects, and try to flee the hard projects, which are often business-critical.
Google is smart enough to realize that employees can often identify bad (and good) projects before the management does, and lets them vote with their feet.