Capitalism drives people to innovate, more than communism does.
Before I begin, I don't hold 100% lassez-faire, cold Capitalist views. I don't believe in the 'Every man for himself' paradigm. I'd even say I have a decent amount of socialist tendencies.
Yet, I'm of the perception that capitalism tends to drive people to want to one-up each other. 'Oh, so Rakesh made a thingamabob? Well, Anjali and the rest of us will make a thingamabob that's more portable and serves good coffee'. Profit tends to be a good motivator for innovation. The drive for people to want to outdo each other (for the profit, duh!) tends to favour innovation more than communism does.
DC power is no innovation to scoff at. However, where I see a communist being content so long as everyone gets it, a Capitalist (motivated by potential profit) could think 'Can I come up with some innovation that's even better and more efficient than DC, rendering my competitor obsolete?'' He'd want to one-up DC power and would come up with...AC power, a more efficient relative to DC in the context of large-scale power supply.