[discodave]

It's the oldest region, which means:

* It's the largest region (ever had an unexpected scaling bug?).

* It has more legacy stuff lying around. For example, old regions have EC2 Classic, while new regions are VPC only.

* There are more customers there. More whales, more use cases.

Most AWS teams explicitly try not to deploy to us-east-1 first, but because us-east-1 is so different on so many dimensions, it is more likely to have issues that dont manifest elsewhere.

(Source: An AWS Engineer)