It is true that you can walk into a shop and get electronic parts. It is also true that you can get PCBs in a shop, but probably pre-made ones.
For serious business, you probably want to ask for samples from serious suppliers. But usually, you will get the parts you asked for on the second day, or within a week or two for a simpler PCB.
It used to be "walking distance" for all electronic components, maybe 10-20 years ago, but since the cost of living has increased in Shenzhen, factories are moving away from the center of the city. But still, if you really want something today, within a 1-hour drive, you can get what you need.
TSMC has a similar work ethic. They have process engineers running experiments 24/7 that each build on the results of the previous shift. When's the last time Intel could hire folks with that kind of dedication in Oregon?
Netflix has a documentary called The Factory which touches on the kind of cultural differences between workers in the US vs China that is rather enlightening.