Being interested in the exchange rate of bitcoin is not just for number go up. Some people already live on bitcoin and seeing their purchasing power in the tank compared to a year ago hurts, because everything costs more bitcoin.
And in order for Bitcoin to achieve the goals of defeating fiat currencies and becoming the world's reserve currency, it must go up in value. A market cap of $380 billion (~$20k BTC) is simply not enough to challenge the inflationary regime.
The price and market cap must go up 100x from here, and it's legitimate to be concerned and interested in the price movements (on a medium and long term time scale at least).
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