Smarter is expensive! The brain will use more calories and cost more. LLMs are drastically less energy-efficient than natural brains. We're one of the few cases where spending more on compute was worth it.

You're describing eusociality, not intelligence. One might argue that ants have completely taken over, but they aren't necessarily smarter than solitary wasps. LLMs only exist because of a huge economy behind them, and it remains to be seen how widespread they'll be once they're expected to generate a profit.