An INVESTMENT is the purchase of goods that are not consumed today but are used in the future to create wealth.
In finance
An INVESTMENT is a monetary asset purchased with the idea that the asset will provide income in the future or will later be sold at a higher price for a profit.
I really don't want to turn these into an economics class but the both definition of what investments are clearly should settle the argument of whether BTC is truly an investment or not.
I have always seen Bitcoin more as an investment than a currency (as a long-term investment to be more precise), and based on both definitions, BTC is clearly an investment. I think some people call it a bubble or don't see it as an investment because they haven't taken the time to learn about and don't understand it.