This isn't unique to any specific region, so I would guess it has to do with density of relevant industries and individuals and the rise of e-commerce. As an e

This isn't unique to any specific region, so I would guess it has to do with density of relevant industries and individuals and the rise of e-commerce. As an example, the San Francisco Bay Area used to be full of shops like Halted, Weird Stuff, Frys (back when they were healthy, not the hollowed out shell that exists today), and Radio Shacks where you could get pretty much any component, module, or development tool that you needed as a hobbyist or small company in the hardware space. What has changed in the last decade though is you can now get access to a much broader range of parts and tools relatively quickly from Mouser, Digikey, SparkFun, Amazon, etc and an even broader set slowly from AliExpress. There are very few places remaining where there is enough density of need in immediate parts, live debugging, or cottage industry-style production to sustain markets like the one in Shenzhen. Worse, decline in one part of the market (dev tools for examples) would result in a decline in visitors and business adjacencies that speed the decline of the other parts. Aside from Shenzhen, I'm only aware of Akibahara (smaller and more consumer focused) and some of the markets in Seoul (one of which is smaller and consumer focused, and the other which is more machining/tooling cottage industry focused).