Mental Rotation
A type of thought experiment or task that is pointless and stupid but seems like it could be useful if its entire purpose wasn't to impress gullible people or deride people for being grounded.
Elon Musk likes mentally rotate objects in his mind. He talks a lot about how he'd like start a colony on mars, but its all mental rotation - there are lots of inhospitable places on earth to trial out such technologies but he's not interested in solving problems, just marketing.