EC2 existed in us-east-1 only for 2 years before it was launched in a second region. Those 2 years were already enough to pick up some legacy cruft and special

EC2 existed in us-east-1 only for 2 years before it was launched in a second region. Those 2 years were already enough to pick up some legacy cruft and special cases. us-east-1 is also the first region for various other old services, like s3 and route53. I think it's also the largest region across many axis, which naturally means it will hit various scaling issues before other regions.