Intelligence being good for you is not the same as stupidity being bad for you.
Of course it is. Intelligence is a scale, at one end we call it stupidity and at the other we call it intelligence. Less of one is more of the other.
But correlation is required for causation. Are you suggesting intelligence is irrelevant to income-earning potential for most people?
I'm outright saying that income-earning potential is relevant to eventual performance on an IQ test. And it's not news, this is a well-known critique of IQ testing. People who use it to try to prove things usually fail.
Intelligence is a benefit as long as it doesn't impede your ability to breed. And it doesn't. It's good in all kinds of situations, even smashing things with a rock. Getting just the right smash on is aided by intelligence.