Because unlike some other providers, AWS understands the value of backward compatibility. They were the first to make the concept of simultaneously deployed versioned public HTTP APIs work seamlessly at scale, and the number of actually impactful API deprecations they have done is tiny. This is one of them.

Prior to this change, IMDSv2 could be enforced on an account, machine image, and launch API call level.

If you're interested in this topic, you might enjoy reading https://steve-yegge.medium.com/dear-google-cloud-your-deprec...