The letters are randomised per AWS account so that instances are spread evenly and biases to certain letters don't lead to biases to certain zones.
The thing is, us-east-1 represents the whole AWS for the majority of us.
Your question reads as a strawman. It matters nothing if EC2 is also available in Mumbai or Hong Kong if by default the whole world deploys everything and anything to us-east-1, and us-east-1 alone.
https://www.reddit.com/r/aws/comments/nztxa5/why_useast1_reg...
Deploying a service to a single region is not, nor has it ever been, "customers don't know how to use AWS".
If anything, cargo culting this belief in global deployments being necessary, specially with services that have at most a regional demand, is a telltale sign a customer has no idea about what he is doing and is just mindlessly wasting money and engineering effort in something no one needs.
This blend of bad cargo cult advice sounds like a variant of microservices everywhere.