Bad thread titles make it harder to find a previous post. That leads to more reposts, which makes more work for the mods. So, I'm more than a little surprised to see a mod come down on the opposite side of this issue.
Sometimes, I like to cite someone else's earlier post on a subject, because there's plenty of clever and knowledgable folks contributing here. If the thread containing that bon mot has an oblique subject, even a simple search can take several minutes.
Using good subjects is really about being considerate to your fellow posters. If a topic is worth posting, it's gotta be worth taking a few seconds to condense the message into a few well-chosen words for the "subject" field.