I don't really see a point of those type of people trying to use Bitcoin to purchase whatever they want since they're already rich. Bitcoin does not have any weight to it when showing somebody the amount of coins they would have, if they show how many paper money that they have then people will get jealous and is more than likely to be controlled by the holder.
You are right. Cash can buy everything and bitcoin doesn't. What is the point of using them to purchase anything? For me, it only good for investment and tranferring funds.. But i think theres a lot of bitcoin enthusiasts which are big names. Not only big names and personalities but also big companies. I think Dell is one of them who jump in to bitcoin.