Before I start, two things:
1: If this is in the wrong place, I apologise and please move it.
2: This post is absolutely NOT a complaint, I'm just curious

I have noticed that on this, and just about every forum, pointless/spam topics get locked (obviously). This is all very well, however they take up space on the boards that could be used by perfectly good topics. Why not just delete tham?

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Because a lot of the time when someone looks for a topic they made and can't find it, their first reaction is to make it again (thinking there's been a mistake somehow). By locking it shows people "this kind of topic needed to be locked" and also, "your topic didn't vanish, it was just not appropriate/not necessary." It also lets the mod explain why the topic was locked, if need by, rather than simply deleting it and people getting confused.

They get pushed down rather quickly anyway but the threads that are still active.

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OK thanks for explaining. Ironically, I think this topic can be locked now!

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Happy to oblige.

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