Yes, but what I am wondering is why one hasn't emerged as clearly dominant overall.
Cryptsy is the most dominant, I think. But it is regional. Some people prefer more localized ones. There are too many coins and the exchanges try to fill a role as being the defacto for the coins that they host. Exchanges are cheap to run and easy to spin up. Cryptos are only about 3 years old. The flood of altcoins are only about 10 months old so expecting a dominant exchange after only 10 months of existence is a lot of ask for. Lets see what happens in 3 to 5 years.