I understand your question and your argument. As health care professionals, even we are not used to this way of working. I have been a pharmacist for 30 years. Personally, I have always thought that a known reaction should not be reported. We report unknown reactions described to us by patients. By unknown reactions, I mean those that are unexpected and not mentioned elsewhere. When such reactions occur, we make a report. Everybody knows that a certain drug might cause a skin reaction.
I have always believed that, in such a situation, my role as a professional is twofold: firstly, to stop dispensing the medication and, secondly, to find a substitute. I know that it happens, but I'm not convinced that all professionals are aware of the need to report known reactions.
Perhaps it is our training that is at fault. We are not taught to make this type of report at university. Perhaps professionals need training on this matter. I am not convinced that everybody fully understands what needs to be reported.