Because they were built over centuries, like natural selection, only the best/most practical survived the test of time. Lot's of rubbish was built as-well, it's just not standing anymore.

Also car centric urban design is IMO inherently ugly (limited options for greenery etc).

built in a time where cost was not really an issue. Human labor was cheap, scale and complexity lower (from an engineering point of view, just add more stones until it looks good), and inflation wasn't really a thing so bulk was possible

Selection bias and natural rock vs concrete.