The Power button is intuitive, and most average consumers are used to turning on something before use. I don't believe it's a hassle or usability impediment. If we lived in a less litigious world, Nissan could simply enable auto-power on when placed in drive/reverse with the brake on for convenience. The big elephant in the room is the safety (liability) standpoint. Taking away a step as compared to other modern cars could open them up for litigation. If they do it like Toyota (which they did), they can ride in under the proverbial umbrella and they can safely state with confidence to the judge/jury: "we did it as per current industry practices" when someone's kid runs over his mom.