It's not about favors. Unions make up less than 7% of the population from over 50% and there is a large quantity of people who want to see the rest of that 7% go away. You're already bargaining in an anti-labor environment and by conducting illegal job actions, you'll lose any good standing with the NMB, your union offers could face jail time, and public perception will take a nose dive. So how does that help you again?