I'll offer three reasons:
(1) Most of the Apple stores in the US are older. The foreign stores in these articles are the newest stores, and benefit from Apple's ever-improving and and increasingly bold design aesthetic. Also, perhaps because of how commerical retain space is configured in this country, fewer of the US Apple-stores are stand-alone creations; and you need a store to be stand-alone to get creative with the achitecture. When Apple has constructed new flagship US stand-alone stores, it has tried to be bold with the design, such as the glass cube store in Manhattan. And remember that this store is from 2016:
View attachment 934653
View attachment 934657
(2) The stores you see in articles about new Apple stores are not the average foreign Apple store, but the best of the best.
(3) Apple probably pays particular attention to these flagship foreign stores, since these act as "brand ambassadors". In the US, people are more used to Apple, so the design of the stores, while important, has less influence.
[automerge]1594975555[/automerge]
There may be some truth to that, but I don't think that's necessarily the primary driver. Consider, for instance, the Apple store in Opera, Paris, which is in a high-income area, yet is stunning. Indeed, I would say that, while the Sanlitun store is lovely (particularly its exterior), the Opera store's interior is closer to what I would describe as "boutique":
When it was first announced, the idea of Apple having its own retail store was not received well by many quarters – here's a commentary by Bloomberg
www.hongkiat.com
View attachment 934652