I think you are very confused with Bitcoin. Bitcoin is an asset, just like your car. Once you sell it, it becomes currency. You can also trade Bitcoin or your car for something else you want by stating a price for each of them. Currently, the Bitcoin price is $26k per coin. So in exchange of 1 Bitcoin, someone can give you his car worth $26k. That surely works as a currency, isn't it? It's modern Gold. You stack it up for a better future.
You are correct that Bitcoin can be viewed as an asset just like a vehicle or any other pricey possession. Similar to selling a car you get a set amount of conventional currency back when you sell bitcoin. It is true that by giving Bitcoin a value much like setting a price for your automobile you may exchange it for other goods or services. In fact the market price of a single Bitcoin coin is currently over $26k and it varies according to supply and demand. Many see Bitcoin as a type of digital gold a kind of safe keeping of value that might one day be useful. Different people have different approaches to investing and some decide to amass Bitcoin as a long term investment.