The old-tech viscous coupling was lossy and difficult to control. Even when you can manually tell the trans to shift (as on a 2009 Mazda5), there is a time delay in the shifting, then you wait for the hydraulic system to confer torque and finally drive the wheels/engine brake.
The modern DCT that high-end cars are using is a direct mechanical connection and uses robotic shifting to do so instantaneously. Shifting is faster than a human can shift an H-gate, and the PID controls on gear selection have better programming etc. due to both the high end nature of the cars and the better systems they're being integrated into.
There is a world of difference between what we colloquially term an "automatic" (slushbox torque converter) and the modern DCT.
But I reluctantly disagree with you. Almost all serious sports cars -- hardly "boring" -- now come with automatic transmissions: * All Ferraris are now automatic * All McLarens are now automatic * Porsche's top street car, the 911 Turbo S, is PDK-only * Porsche's top track-ready car, the 911 GT3, is PDK-only * The fastest hypercars, the LaFerrari, the McLaren P1, and the Porsche 918, are all automatic (I recall all 7-speed dual clutch)
Even Lotus, the one company you'd expect to keep the manual faith, on lightness grounds if nothing else, made the Evora available a few years ago with an automatic transmission. And Porsche has been quoted as saying the manual transmission may no longer be available after the 991 is phased out: http://www.autoguide.com/auto-news/2012/02/porsche-911-manua...
Unfortunately manual transmissions now make the car slower. A stick is becoming an enthusiast's conceit, C&D's campaign notwithstanding, and I hope they're still offered, but I'm now considering a dual clutch automatic for my next car.