Then dealers would have a floor full of bikes that won't sell.

Barcons are all that you suggest - inexpensive, functional, uncomplicated, reliable. But they are a niche market, relatively speaking. STI/Ergo is more complicated and more expensive - but it is very efficient, easy to use, and very reliable, too.

I like my vintage bikes, and have three very nice ones with friction shifting. But for every day riding and especially long distances, the new stuff almost always gets the nod. It's too much better not to.