Its MONEY people. The absolutely beautiful brazed lug frame went out of style because of money!!! It is cheaper to throw tubing into a fixture and have a robot weld them. This goes for both steel and aluminum.
But then we also have the carbon frames. The manufactures have brain washed the "real cyclist" into thinking they HAVE TO HAVE a carbon frame. Once again it is money. The manufactures can contract with some company in China that pay poor Chinese women to lay up a carbon frame, paying her probably 75 cents an hour. Thru channels they end up in you local bike shop and sell to the well heeled for $5000 and up. Money money money!!!!
I would really like to know just how much it cost a bike company in China to lay up a carbon frame bike. I would be willing to bet it is not very much.