I suppose it was to show how much he believes in his own product, if he demonstrates that he trusts it to drive him around safely. When you see an "inventor" testing their own product it is usually good press. Given, I realize he is not the "inventor" per se (more of the "enabler"?), but still it is a show of good faith in one's own product.
Not because of hero worship.
I can't say I've ever seen a video of Elon riding in a self driving Tesla before, seems like it would be very tangible proof how much he trusts the autopilot.
