I feel like age shouldn't factor in, only location. Granted expenses will be different based on age, but they don't seem to be using expenses to determine "rich-ness" at all.
Age is strongly correlated to income. People with experience generally get paid more. It's not particularly useful for a 25 year-old to compare themselves to a 55 year-old.
Well sure, when talking about experience. But not wealth. A millionaire living in my city is objectively wealthy regardless of age. I'm not "wealthy" by any means. Despite that, my income is top 1% for my age-group. However the median income for my peers is also barely above minimum wage, so thats not a terribly helpful metric. Knowing I'm in the top 11% regardless of age is far more helpful in understanding how I fit into my local community.