Aside from
@jeepinmatt 's point about energy loss through the torque converter, the key to all this is manual-mode automatics. You get he best of all worlds, minus maybe the fun of physically throwing your arms through the gears.
As mentioned the real problem with autos is that they are reactionary, and don't have the power of a human brain behind them to predict ahead of time what the gearing needs to be so you don't have a loss, like when you're making the change between downdhill and uphill and want to be ahead of the lug, and in the power band already when needed.
You also can't compression brake to slow down coasting to a light etc.
But, you CAN do all that with an auto in manual-mode...
Also, you guys have to realize that in the not-too-distant future the same AI tech used for lane deviation and collision avoidance etc will also be applied to the transmission, so it can and will do the above things for you.
I love the manual in my car, and specifically ruled out any non-manual car for my DD, solely bc to me it makes driving more fun. I don't pretend that it makes me faster or gives better fuel economy, because it doesn't... I just like the physical interaction with the car and the "feel" of rowing gears. I hold no bones about the fact that this will eventually be deemed 100% unnecessary, and in many ways already is, I just admit it is purely for my own happiness.