Population density has some serious advantages. Convenience is one of the biggest. In Korea, you can get almost anything really, really fast.
Delivery food here goes far beyond anything we've ever experienced. We can order fried chicken, soups, sandwiches, Chinese food, a wide variety of traditional Korean foods, and of course pizzas. And someone is always putting a new booklet of delivery options on our apartment door.
But beyond food, we can literally walk across the street and do 90% of the various things we need to do in the week: banking, dry cleaning, grocery shopping, etc. And the dry cleaners actually deliver our clothes to our door for no extra charge!
Also, because Korea packs the population of California into an area the size of Indiana, and further packs the people even more into city clusters, (something like half the land is mountainous and not easily "livable), all forms of delivery are extremely cheap. If you make an internet purchase, it will probably be at your house in 1-2 days for less than $3. We bought a toilet online - yes an actual ceramic toilet - and the total shipping was about $7.
One more reason why I love this place.