most people use it for investment, not for payment methods.
And Bitcoin only applies as a commodity, it cannot be used as an official currency.
I would agree that most people use it as an investment, but it's not a commodity like sugar or pork bellies are.
Bitcoin is strange. I think of it as an extremely volatile currency that people are reluctant to spend because they fear missing out on potential profits. If the purchasing power of the USD fluctuated like bitcoin, there would probably be a lot of people saving more money, hoping to profit from the volatility.
The big thing IMO is that most merchants don't accept bitcoin, and most people don't receive their paycheck in bitcoin. If you want to buy something using crypto, you pretty much have to go out of your way to acquire it first--and a rational person would not do that. That said, I've spent bitcoin that I've earned from signature campaigns, but I think a lot of people who earn bitcoin tend to exchange it for fiat because their options for buying stuff increase dramatically.