So instead of coming to terms with your fellow workers you rather have them fight capitalists by themselves? Leave them to the scraps the bosses deem sufficient while you're wheeling away a wagonload of concessions won through your unique bargaining power?

You're limiting the strength of worker's. If train conductors don't strike for train toilet cleaners noone will.

And any opposition between worker's interests is negligible compared to that between workers and capital, who have no interests in common at all.