I agree to a point, but isn't this part of human nature as well?
Just think about how a conversation goes when people get together and chat. They wander from topic to topic, sometimes coming back full circle to what they started talking about.
I think different people have different ideas about what "related" is, and something that doesn't seem to be on topic at first might just spark some ideas to help the "OP" out with their "OT" (creative license: "original topic", as opposed to "off topic").
Some of the threads that start out with a question that could be answered with Google and 30 seconds of any computer illiterate person's time actually get more interesting as they go farther and farther off topic.
There are definitely limits to this logic, but this is one of the best forums I've ever found to find threads that DO stay on topic and do so in a very respectful manner. I don't think I've even once seen the acronyms "GIYF" or "RTFM" here, although it may be tempting from time to time, sometimes even warranted.
That reminds me of a great recipe for pumpkin pie that I thought you'd all enjoy:
2 cups pumpkin
3 eggs
<insert sly smirk>
-Sparky