I can't blame him wanting to retire. Look at the injuries and fatalities in the top flight motorbike sports. In the last 12 months alone 2 riders have lost fingers, 1 rider has died, 1 is in critical condition (get well soon Juan), several are riding/have ridden with broken limbs...
The guy has millions of dollars, a beautiful wife, a new kid... That seriously affects your motivation. It's not like he doesn't push, it's not like he is in a sport where you can play safe and pick up a pay check.
He could retire from racing and still get to play with bikes for the rest of his life, and get paid for it, and not have any of the risks. He is unlikely to equal Rossis 7 top flight championships, but he will always be the most successful rider in the 800CC era...
All of us sat at our keyboards look at his life and think it must be amazing, but you have to temper it with all the downsides, and with a young child etc, the number of downsides, and the stakes of the game have just gone up.