Why does AI suck at Excel?

I've been playing around with using Copilot and Claude for building models in Excel, lately.​As I've been playing*, I've noticed something:Using AI can really speed up some building.Some of my favorite prompts so far:"Can you make the model formatting prettier?""Can you review this whole model and tell me where there may be mistakes?""I want to use this model in a demo. Can you sanitize it of any identifying data?""I'd like this revenue forecast to be based on a marketing funnel. Can you build me a marketing sales funnel tab and use it to calculate new customers each month?"The power is incredible. I could save so much time!But there's a huge downside:I can't trust the output.​Some examples of mistakes I've discovered (which doesn't include the ones I'm still unaware of):It sometimes uses insane formulas that are heavy, really hard to understand, and overbuilt. Eg. a million nested…

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