I am not so sure Pope Francis is humble and this appearance of humility is not instead scruples. The Pope should not pay his own hotel bill. The Pope should not wear simple clothing. The Pope should not ride in a bus instead of taking a bulletproof car.
Seems more likely that he's attempting to follow St. Ignatius' advice: "The despising of one's self in the midst of honors and riches, and disdain for all glory, should be esteemed more highly than corporal mortification."
We can't expect a Jesuit who's spent half his life immersing himself in Ignatian spirituality to abandon the results of his spiritual formation in response to being elected Pope.
I disagree. He will eventually learn to wear the trappings of the papacy well, but still in his own way.