Vaccines are expensive to research and require a very long period of trials before being release to the public, while this happens people will die by the millions without antibiotics.
Also because bacteria can mutate making your vaccine useless, so you need to research again.
sure. did you get your flu vaccine last year? will you get another next year, and the year after? You should, but there is a limit to the number of the vaccines that are feasible either scientifically, clinically, or economically.
But when bacteria become too dangerous why we don't simply vaccinate against them?