[jtokoph]

While I don’t agree with the implementation, I think this is usually done on forms that ask you to confirm the value a second time. The goal is not to prevent you from pasting from an accurate source; instead they are trying to prevent users from copying an incorrectly manually typed value from one field to the other. The end result just also blocks our use case…

[afiori]

sometimes websites forget to disable selection dragging, so you can paste in the first field and drag to the second field.