Every new technology is always received with resistance by some. I'm sure when pneumatic tires were introduced for cars, some people said "What happens when the tube goes flat and you don't have a pump?" My wooden wheels have worked fine, why should I change?
I got my first Di2 back in December of last year and don't expect I'll ever buy a new bike without electronic shifting again. Ease of shifting, synchro shifting, no cable replacement, etc. A don't expect to ever catch myself with a discharged battery and I'm not worried about it failing and stranding me somewhere. I know that it's possible but probably no more so than being stranded by a mechanical issue.
I had a 3 X 9 105/Ultegra setup before and was perfectly happy with it till I tried Di2. I won't miss anything about it. I also do not miss points and distributors, or carburetors, or downtube shifters