What if it were only a daily update? Once a day, say, 12AM, it'll update all the stocks? Would we be able to withstand that amount of lag? Say we even just incorporated it into one of those "quick restarts" that took a few minutes.
Er, because most of the players on ECC are kids? So logically, the can't do that. I know when I was a kid the concept of the stock market used to entertain me. If we could get it to work properly, which is a big if, then I'd love it to be here. However, I fear it would only be another form of gambling which is far from what the real stock market is.
For the same reason websites like this exist. People have virtual money, but not everyone has real money that they can invest. It's just another potentially fun addition to an economy server.