e.g., your underlying assumption may be a little off. I don't think they're TD'd because they don't fit the current categories (we could always put them in General, if nothing else).

They are TD'd, because the general consensus is that the particular problems lack critical thought and/or are too well known and/or are easily looked up and/or they aren't appropriate for the site.

standard disclaimer: as always... I could be wrong!

The general reasoning behind not accepting lateral thinking is that they don't fit the format of this site. Lateral thinking questions are generally need question answer hints, which doesn't work out with the comment format in Perplexus. This was decided long before I came to Perplexus, but you might find one or two lateral thinking problems that were posted before this decision. These few puzzles probably caused the decision in the first place.

See, it's not because we don't like lateral thinking puzzles, though you probably will find that most of the upper-ranking people don't like lateral thinking puzzles anyway. Perhaps lateral thinking people don't stay around Perplexus as long ... ?

Now, if we were to add a category, I think we should add "Combinatorics." There have been a bunch of these recently (More archery practice, Merit review, FIGURE it out) , and I myself have a few in the queue that are currently just in General.