I have not been around here as long as some others, but what I did notice:
1) Much (most?) of the time, the question is similar, but not identical, but a lot of us don't bother to read the OP very carefully or may not appreciate the difference. After seeing similar questions a number of times, it is perhaps natural and undsrstandable to start to assume they are all the same, our brains are wired for pattern matching. And, if you start with the assumption that it's all the same, your perception is selective and biased, and of course you will see a confirmation of it everywhere. Our brains are wired this way, too.
2) Often (usually?), many (most?) of the replies are responding to a question that's similar, but not identical to the question stated in the OP. I think a lot of the time, when people hold a strong opinion on some subject, they need to express themselves, and may end up bringing up the same point across a number of threads, regardless of the exact topic, especially if they think it's the same question over and over (see above).
When most threads steer a bit off-topic, if ever so slightly, and contain some amount of tangential discussions and knee-jerk replies, the practical utility of the "search" button can be somewhat limited.