Again, it is about relativity. He is humble compared to the other Cardinals who probably all have drivers and cooks. Just because you and I actually enjoy driving and cooking, doesn't mean everyone does. And it really falls down to his motivations. Is he doing it because he enjoys it/wnts to, or is he doing it because he feels compelled to put on a show. If the former, it can be a form of humility just as my growing my own apples, pears, lettuce, and cucumbers could be viewed that way. I partly do it to get closer to God, partly becaus eI love working with the earth (it is so the opposite of what I do 8 to 5 M-F) and partly because I enjoy eating the fruits of my labor as well as sharing them with my family, friends, and neighbors. Technically, that makes it a humble part of my lifestyle. But if I did it to try and appear humble, then I wouldn't be by any means.
To those who put on the airs of humility, they get their reward, adoration here on Earth. But those who do it not to appear humble but because they enjoy doing it and feel it brings them closer to God, they store up their rewards in heaven.