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Bitcoins are perfect example of a thing called Giffen good where as the price raises the demand gets higher and as price drops so does the demand. That's a thing that doesnt follow normal rules in economy and that is why economists dont agree that Giffen goods exist.
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Bitcoin is a currency -- money. Not goods.
Yes, the more money is worth, the more people want it. All money, not just bitcoin. Price of goods rising is the exact opposite of the price of currency rising. If a bitcoin is worth twice as much today as it was worth yesterday, of course people would want it more -- it buys twice as much stuff (goods). That's not called Giffen, that's called common sense. And that's why it helps to know a bit about economics.