Now that a lot of the trading is done electronically why does trading on the "physical" stock exchanges (such as NYSE) still exists? Does every NYSE listed stock sale really go through a trader on the NYSE Floor?
For the second part, no most NYSE trades are done electronically.
Non-electronic stock exchanges still exist because they used to exist. There are a lot of people in trading firms who grew up with floor trading and don't want to give it up, either because they feel more comfortable with it or because they might lose their job if they went away from it.