I remember back in 2017 when crypto was getting mainstream there were a few of those small used car lots or buy here pay here places who places Bitcoin accepted logos.
A buddy of mine actually had BTC and was in the market for a new car. When he tried to buy it the price went up like 10% because of the extra transaction and conversion feee. Basically passed on the deal because he could sell it with his exchange for like 0.25% at the time.
So nobody actually buys cars with Bitcoin.
Then it comes the issue of Elon Musk himself, do we really want to help him out when he has done so much damage to the market? Quite honestly even if I had the money I am not willing to help him out and give him even more profits and more bitcoin just so he can exert even more manipulation to this market, as he has shown that he is not above trying to manipulate it to get his way.