That's fine where you have choices of where to go. A lot of the heavily unionised workforces don't have that choice - a change of job necessitates a career change and dropping to the bottom of the ladder again. So I can see why people are keen to fight back.
It's not like a train driver operating a particular class and on specific routes can walk into an equivalent role within a few weeks of deciding they dislike their current employer.
Granted this applies less to station staff roles, but it's likely that any change of employment for them would come with a large drop in earnings and benefits, so it's worth fighting for if that option exists.