Most often, people just won't be interested in the problem, and will ignore you, hoping you and the problem go away, at which point your default solution wins and is documented. But every now and then, it'll set alarm bells ringing up and down the chain of command, and THAT is why you bring it up.
Of course it's also important to get a feel for what kinds of issues should be brought up, and what issues should just be quietly solved. This skill is half-technical, half-political, and comes with experience.