This is Google Maps in a trenchcoat, and I’m glad you bring it up. In its heydey before things got weird, Google Maps pioneered the practice of clearing a “donut” around a major city, improving legibility. While I don’t favor baking specific presentational choices into the database, I appreciate that the urban areas force us to consider a similar “sphere of influence” around an urban core.
By some measures, it’s totally unfair for us to subordinate giant places to even gianter places while cutting punier, more distant places some slack. But the settlement-related place=* values become more useful when they can communicate something about the relationships between places. Some maps will use this classification scheme to establish better information hierarchy, while others will eschew it in favor of a scale based on population alone, in order to simplify the legend and make labels more predictable. Both approaches are valid in the hands of a map designer, as long as the population figures are based on something realistic like UAs.