Life is not so simple, there is a lot more to a advancing a career than give me money or else. If times get hard I dont want my hire date causing me to be let go if I am more benificial than someone hired before me. I want to be able to raise the team around me. I want to be able to lead and improve a team. I have no issue with my Boss replacing me, I know my value and worth. I will do my best to make him see that. I don't need the support of the group, I will happily give my support to the group. I personally do not see value in a union. I like to be assesed as an individual but it has nothing to do with fuck you I got mine. I do not make threats to get ahead in the world and would never be part of a group that does. You looking at this in such an us vs them, that is not how I operate.
So what do you do when the value you see in yourself and the one your boss sees in you differ? Work harder and hope senpai notices you? You're ok with your boss replacing you with a more willing employee, even though the work you are doing is good? You have too much faith in the system.
Nothing you describe is prevented by unions. Unions are here to help you when bad times happen. Like after working for 30 years for the company that suddenly wants to lay you off. You don't think long time works should be given incentives for their long term dedication? You don't think they should be protected a little bit more because how difficult it is to find a job at 50?
Unions don't prevent bad workers to get fired, they prevent
all workers to be fired for inane reasons and without given due credit. If you're shit at your job, you'll get fired, union or not union. But with a union, the company has to actually spell out what bad worker means to them, and isn't just a way of getting rid of someone for whatever reason (like, he
wants more money sees more value in himself, or he wants to start a union, or he ruffled the feathers of some higher exec)