Given that the ones posted here are often programmer-related (ie, the UniXKCD), why not? Far more inane and less-geek-related things are posted year-round, and at higher rates, and they get attention too. I'm not saying this is good or bad for HN, but they're clearly interesting to the inhabitants, so there's definitely a valid argument that that's what's best. And arguments against. Bah, whatever.

I, however, wouldn't oppose a "[A1]" (or similar) tag prefixing April Fool's threads, and would happily modify my lonely submission if people would prefer.