Why is doggy daycare only a viable business in certain neighborhoods? Dog owners who can pay are common; dog owners who can pay, need daytime care, and live nearby are much rarer. Cities concentrate specialized buyers, not just wealth.
In Los Angeles, dialect coaches and location scouts can make a living. In Boston, lawyers and investors can specialize in one narrow area of biotechnology. Food and shelter can be provided almost anywhere. Rarer services need the right people nearby.
Many countries have tried to cargo cult Silicon Valley or Shenzhen by wiring fiber into glassy office campuses. But the secret sauce of industry lies in well-matched weirdos; a petri dish where founders and engineers and suppliers and customers mix.
For the same reason, the appearance of one bike lane or wine bar is not enough evidence to declare the Decline and Fall of The Good Old Days. An amenity becomes part of a neighborhood only when enough people nearby can support it repeatedly.
The founder who converts a warehouse to a sourdough bakery is taking a leap of faith when success is not guaranteed. The hundredth crumb chaser is marginal, but no less important to progress at the frontier. It takes both types to ferment a unique place.