There are unscalable practical barriers to seeking consent from the whole population. There are 60 milion of us, after all. It is a far bigger undertaking than the census, and it is hard to imagine it ever happening. It would be far easier to legislate to protect the work of cancer registries and other organisations concerned with epidemiology and health services research, to ensure that the confidential data they need could never be used for non-medical purposes. That would protect the public and promote new medical knowledge.
Epidemiology is the foundation on which all preventative medicine is based.
Without it, much would be just anecdote and small drug trials. This move to tie its legs together can only be motivated by some unthinking adherence to an abstract philosophical doctrine about privacy. The point of the principle of confidentiality was to protect the patient from untoward disclosure of information which could be used to his or her detriment. It should not be a moral absolute, at so great a cost. I'd rather have another birthday, thanks.