I'm repurposing a meme where someone asks something like "Why didn't you ___? Are you stupid?" Basically I'm wondering about the answer to the first question,

I'm repurposing a meme where someone asks something like "Why didn't you ___? Are you stupid?" Basically I'm wondering about the answer to the first question, but the utter absence of any explanation of it makes me wonder if it's common knowledge, and so I also wonder about the answer to the second one.