Bitcoin is not a necessity and there are no government rules or policies citing that we really need to use bitcoin. So bitcoin usage is voluntary, in your case you use bitcoin to buy car is not absurd but a valid resoning. As for me, I want to become rich and have an extra income. Bitcoin for me is one of the most promising currency compared to fiat currency, it has been doubling its value for several years now and it is continue to increase and I believe that keeping at least 1 btc will give me 1 million dollars 5 years from now. At this point of time, as mentioned above, it provides me additional income even at home. More power to bitcoins, if it is not a need today but it will be a need in the future.