Imagine copying via Ctrl-C and having to hit enter to confirm a dialog "Did you want to copy this text". It's added, unavoidable friction for an action that some people use a lot.
Additionally, some actions on top of the original behavior (that depended on Ctrl-C completing automatically, to keep with the analogy), now are just broken.
While I appreciate the analogy, it's important to note that registers are a fairly advanced feature, not quite as ubiquitous as Ctrl-C. Standard Emacs copy-paste remains unchanged and functions just as expected.
Additionally, some actions on top of the original behavior (that depended on Ctrl-C completing automatically, to keep with the analogy), now are just broken.