Pathetic's demotion to junior-school status is fairly recent. Eric Partridge included it in his slang dictionary in 1937, defining it as "ludicrous", but before that it was always a noble word, good for indicating compassion, rather than contempt as it does now. Heroes died pathetically, readers were moved by a pathetic line of verse, and one of Beethoven's more affecting sonatas was called the Pathetique. It all started with pathos, the Greek word for suffering, which, unlike pathetic, is still used for serious purposes. It's true that a dog that raises a pathetic paw may make you sorry for it, but not, I think, a man who raises a pathetic hand. The old use survives in the "pathetic fallacy", a phrase still found in critical journalism, and hardly anywhere else.
How can this have happened? It's a puzzle. The same fate long ago befell pitiful, an ambiguous word which could be either about kind and merciful people who pitied others, or about those who deserved pity themselves, but now it nearly always means the latter, and there's not much kindness or mercy about it any more. Perhaps everyone is getting more hard-boiled. In young Queen Victoria's time, men wept easily in public and were not mocked. But when an Australian premier was seen crying on television a few years back, many people said he was rather pathetic. And they weren't being kind.