Why do the union’s asks need to be reasonable?
They don't. The unions can ask for the most unreasonable concessions they want. They shouldn't be surprised if they don't get them though.
Regarding the ILA:
They can demand triple their current wages if they want, but people get to call that unreasonable and say they don't deserve it. Or just laugh at them.
They can demand a ban on port automation, but the rest of us can shake our heads at their selfishness (remember - ILA = I Love America) at wanting to put us behind Third World countries so that they continue to be journeyman abacus operators while the rest of the world uses computers.
They can strike, with their leader publicly stating that he wants to "create a national crisis", and then actually create a crisis that puts lives at danger because they chose to strike in the middle of a national disaster where supplies they process are an integral part of saving lives. They could have created good PR and public goodwill by, immediately after the hurricane hit, stating that they were suspending their strike until response efforts have wound down (because ILA = I Love America). Instead, they continued their strike and wondered why we were all disgusted with them. The only reason they have now postponed their strike is because of the hate they received for fist pumping to "create crisis" while people were dying.
So make all the unreasonable asks you want, but don't be surprised when people are disgusted with you for it.