That's absolutely something you can configure your S3 bucket to do if you want (I have one of mine replicating elsewhere).

The amount of data S3 stores "automatically replicating" to other geographical locations would make things prohibitively expensive, especially when you consider the daily delta, and how much of that is ephemeral or frequently mutated data that is stored. The bandwidth costs alone would be eye-watering, let alone the storage costs.

S3 cannot make any automated decision about whether data is, or isn't important, and if they did they'd only open themselves up to lawsuits if they guessed wrong. That's why it's made an option for the end user to enable replication if they want to, or choose to replicate their own data.