Why is Katowice so obscure?

[mpbond]

Sometimes the Pearl River Delta is considered the world's largest metro area with 85 million people. Now of course it has 2 very famous cities Hong Kong, and Guangzhou, better known to English speakers as Canton.

That could be more comparable to the Northeast Megalopolis in the US. A mostly continuous set of urban areas anchored by very well known cities (Boston-NY-Philly-DC), but with the vast majority of it's ~50 million residents living in much less well known places.