If altcoins were never made, I suspect that bitcoin would not grow so much either. Part of the altcoin trading is that altcoins are used to be exchanged from and to bitcoin, then to local currencies. If altcoins did not exist, demand for bitcoin and awareness of people is lesser than we had today. Who would want to buy something that cannot be seen and can only be traded to USD or your local currency? People would just trade in Forex instead. That's why altcoins still has part on where bitcoin today is.