I'm against the sites because all they really do is take advantage of newbies. People come in here ready to invest money into BTC and go blind with the possibilities.
Then you are against all gambling sites because they all are doing the same. There is really no difference between gambling and ponzi because in both games are losers and winners. As long as its not a scam that is.
These "services" add nothing, where as the other things you mentioned like cars, paintings, houses are actual things that can be used when bought.
Well some people like to play them, i dont know if you noticed. As for expensive paintings or old cars? They are often hidden in safe places like paintings or not used at all like old expensive cars. People are buying them because they know its price will rise because of limited amount. How is that different than ponzi scheme? I know you can still sell this with a loss but there are also chain games that refunds your virtual item if you wont sell it like this one
btctreasure.com