But Krugman is wrong to say that Bitcoin serves no economic purpose. Speculation is a valuable product, and one that has been in existence since human beings started trading with one another thousands of years ago. Bitcoin, as a meme investment, is useful for people, and will continue to be useful for people--as will meme investments in other cryptos, and other digital currencies.
And you are wrong as well.
Bitcoin is not for speculation. It is also not a "meme investment".
Bitcoin is a currency and a sophisticated payment system that is working globally and 24/7 without ever shutting down. That gives it the value that goes up and down then it attracts investors who see it only as an investment.