I then compare them. I see they are the same. no mistakes were made. we know that with 100% certainty. No need for any checksum. The eyes are good enough.
The checksum is not meant for you and your eyes. It is meant for the application so that whenever a user enters the checksum incorrectly into that tool's textbox it can automatically detect if there were any mistakes in the input so that the application can inform the user that something is wrong.