I have read the threads and it's really complicated yet sensible topic. I have not heard that it is really possible to buy car using bitcoin and its really interesting. i have seen comments and options on how to buy car if using bitpay or if converting your bitcoin to cash or saving it to your bank account. I've been customer service in a large bank company in US and its really true that IRS really investigates the money in ones account.. where did you get the ource of funds, what are your jobs, do u have any properties, do you have family, how many children do you have. It's really time consuming if youre going to place your bitcoins earning then convert to cash then saves in your bank account. Then suddenly IRS or local tax can request to place hold in your money. I understand those account holders who complains when their money were placed on hold.. Though I understand the bank and IRS to protect any fraud however it consumes a lot of time and affects if you have pending transactions like buying a car.
While the BTC transactions (BTC to fiat/fiat to BTC) are low there isn't problem, the government won't be watching you, but once you starting transacting high and moving money to buy for example a car, the scenario changes... But it's still possible and there wouldn't be problem if someone have his income exclusively from the internet without passing through the government's eyes.
Then this person must send the BTCs to the seller and get the car. I just don't know if there were any problem with the government when trying to legalize the car documents.
I just spent the last 24 hours talking 44 different car dealers and from half of them in each and every one of them is more than happy to take Bitcoin. I don't know why you have trouble doing this because all you have to do is pick up a phone. Also it depends in which part of the world you live. Maybe the OP lives in that part of the world where bitcoin is not easily acceptable. 
