At least for those people with say less than 10 posts.
There is no end of dross from people bumping threads with 1-line of pith which is either off-topic, or just vaguely relevant.
Most seem to go for old threads with high "visit" counts in the belief that means their sig will get more visits that way. Most are incapable of doing the math of "thread age / visits".
And you just know they're doing it just to spam URLs in signatures to push whatever they're selling.
Most never return after their initial flurry, figuring they've either been banned or the posts have been deleted. In any event, they're onto the next forum to repeat the process.
They're certainly NOT here to make a useful contribution!