That would be something they should discuss. Instead, by striking and getting what is a well above-average salary, it could be argued they are perpetuating the suffering of future workers to have to put up with those conditions, on account of having created a very attractive 'pull' in the form of a good salary.
There could perhaps be some way of bringing in automation, moving existing employees into different roles for the remainder of their careers and therefore satisfying both aims.
Instead, from the outside, the tube unions seem to go on strike every other month. I don't see my water, gas, electricity or internet connections being switched off because workers at those companies are striking. Tube workers seem more than happy to inflict financial damage and inconvenience on the other 8 million people who live in London and who depend on them. Apparently they don't care that their actions are likely to be having a much more damaging impact on those Londoners on average salaries (as well as the large numbers on below average salaries).
I know someone on the breadline who works all hours and makes an absolute pittance. One day of not being able to go to work for someone in such a situation can literally risk their job, rent and ability to feed themselves.
I find the actions of the - by comparison wealthy - Tube unions generally disgraceful.