Is it right to ask university and job applicants their ethnic origin‪?‬

The second day in the university, I wanted to register with the medical centre. I had to fill in a form asking me about my address, previous diseases and allergies. At the bottom of the page there was a field where I had to tick a box confirming which ethnic background I had. I considered the filling in of that form to be up to my own knowledge and conscience and as I had never been asked such a question before I left the box blank and handed the form to the lady seated at the desk. She scanned through what I had filled in and gave it back to me: “You must fill in your ethnic origin,” she said. I told her I did not know what my ethnic origin was and that I had never been asked that before – not mentioning that I was utterly confused by the many choices I had. Of course, I knew I was white. But I was not ‘White English’ or ‘White Scottish’ or ‘White Welsh’, which was certain. She said: “You are from Germany? So you are ‘White Other’.” Now, that really killed me. I ticket the corresponding box and discomposedly went outside, wondering what difference it would make to define my ethnic background this specifically. And, if she knew I was from Germany and thus my ethnic origin was ‘White Other’, why did I have to tick the box then? Can’t she guess it herself? What was the use of that anyway?