For local workspace HTML, default basemap disappearance starting with CesiumJS version 1.109

While working with CesiumJS Quickstart tutorial, I recently notice that there happened a CesiumJS version incompatibility starting with version 1.109.

According to the tutorial guide, I used to copy the tutorial code to create a HTML file and view it in a browser. But since v1.109, the default basemap (Bing Maps Aerial) doesn’t appear. If I change the CesiumJS source CDN version back to v1.108 or earlier, the basemap shows alright.

Apparently, CesiumJS v1.109 or later version doesn’t support local workspace HTML visualization in a browser without a local hosting server. Why is that? What was the background to stop the long-term supporting feature?