Remind me - when was the last Ryanair accident?
Easyjet?
Air Berlin?
Wizzair?
Norwegian?
Southwest?
Jetblue?
Air France?
Briefly - air transport in general is subject to incredibly rigorous regulatory oversight and the regulators will come down like a ton of bricks on anybody bending the rules.
Plus for airlines with a very strong cost-control culture, any accident or major incident which even hinted at cutting corners could spell commercial disaster. Anybody remember ValueJet? - in its day the world's most profitable airline - driven out of business by a crash and other safety issues (I know, they survived, sort of).