Why does anyone use MtGox? Why would anyone buy BTC using MtGox when the price is so much higher than other exchanges (e.g. CoinBase)?  And why would anyone sell using MtGox if you have to wait an outrageous amount of time to withdraw the USD?  In other words why is MtGox getting any business at all?
The sole and only reason to buy there, is because you already have fiat stuck there and you want to get it out ASAP.

About selling, if you are optimist you can say that some people value that the risk of Mt.Gox defaulting plus the time they have to wait without their money is less than the price difference with the other exchanges.

If you are pessimist, you could say instead that they are simply stupid and do random things without really thinking about it.

Still, since there's no reason at all to send fiat there to buy BTC, yes, I agree it makes no sense for Mt.Gox to be still in business.